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PERLFUNC(1)	       Perl Programmers	Reference Guide		   PERLFUNC(1)

NAME
       perlfunc	- Perl builtin functions

DESCRIPTION
       The functions in	this section can serve as terms	in an expression.
       They fall into two major	categories: list operators and named unary op-
       erators.	 These differ in their precedence relationship with a follow-
       ing comma.  (See	the precedence table in	perlop.)  List operators take
       more than one argument, while unary operators can never take more than
       one argument.  Thus, a comma terminates the argument of a unary opera-
       tor, but	merely separates the arguments of a list operator.  A unary
       operator	generally provides a scalar context to its argument, while a
       list operator may provide either	scalar or list contexts	for its	argu-
       ments.  If it does both,	the scalar arguments will be first, and	the
       list argument will follow.  (Note that there can	ever be	only one such
       list argument.)	For instance, splice() has three scalar	arguments fol-
       lowed by	a list,	whereas	gethostbyname()	has four scalar	arguments.

       In the syntax descriptions that follow, list operators that expect a
       list (and provide list context for the elements of the list) are	shown
       with LIST as an argument.  Such a list may consist of any combination
       of scalar arguments or list values; the list values will	be included in
       the list	as if each individual element were interpolated	at that	point
       in the list, forming a longer single-dimensional	list value.  Commas
       should separate elements	of the LIST.

       Any function in the list	below may be used either with or without
       parentheses around its arguments.  (The syntax descriptions omit	the
       parentheses.)  If you use the parentheses, the simple (but occasionally
       surprising) rule	is this: It looks like a function, therefore it	is a
       function, and precedence	doesn't	matter.	 Otherwise it's	a list opera-
       tor or unary operator, and precedence does matter.  And whitespace be-
       tween the function and left parenthesis doesn't count--so you need to
       be careful sometimes:

	   print 1+2+4;	       # Prints	7.
	   print(1+2) +	4;     # Prints	3.
	   print (1+2)+4;      # Also prints 3!
	   print +(1+2)+4;     # Prints	7.
	   print ((1+2)+4);    # Prints	7.

       If you run Perl with the	-w switch it can warn you about	this.  For ex-
       ample, the third	line above produces:

	   print (...) interpreted as function at - line 1.
	   Useless use of integer addition in void context at -	line 1.

       A few functions take no arguments at all, and therefore work as neither
       unary nor list operators.  These	include	such functions as "time" and
       "endpwent".  For	example, "time+86_400" always means "time() + 86_400".

       For functions that can be used in either	a scalar or list context, non-
       abortive	failure	is generally indicated in a scalar context by return-
       ing the undefined value,	and in a list context by returning the null
       list.

       Remember	the following important	rule: There is no rule that relates
       the behavior of an expression in	list context to	its behavior in	scalar
       context,	or vice	versa.	It might do two	totally	different things.
       Each operator and function decides which	sort of	value it would be most
       appropriate to return in	scalar context.	 Some operators	return the
       length of the list that would have been returned	in list	context.  Some
       operators return	the first value	in the list.  Some operators return
       the last	value in the list.  Some operators return a count of success-
       ful operations.	In general, they do what you want, unless you want
       consistency.

       A named array in	scalar context is quite	different from what would at
       first glance appear to be a list	in scalar context.  You	can't get a
       list like "(1,2,3)" into	being in scalar	context, because the compiler
       knows the context at compile time.  It would generate the scalar	comma
       operator	there, not the list construction version of the	comma.	That
       means it	was never a list to start with.

       In general, functions in	Perl that serve	as wrappers for	system calls
       of the same name	(like chown(2),	fork(2), closedir(2), etc.) all	return
       true when they succeed and "undef" otherwise, as	is usually mentioned
       in the descriptions below.  This	is different from the C	interfaces,
       which return "-1" on failure.  Exceptions to this rule are "wait",
       "waitpid", and "syscall".  System calls also set	the special $!	vari-
       able on failure.	 Other functions do not, except	accidentally.

       Perl Functions by Category

       Here are	Perl's functions (including things that	look like functions,
       like some keywords and named operators) arranged	by category.  Some
       functions appear	in more	than one place.

       Functions for SCALARs or	strings
	   "chomp", "chop", "chr", "crypt", "hex", "index", "lc", "lcfirst",
	   "length", "oct", "ord", "pack", "q//", "qq//", "reverse", "rindex",
	   "sprintf", "substr",	"tr///", "uc", "ucfirst", "y///"

       Regular expressions and pattern matching
	   "m//", "pos", "quotemeta", "s///", "split", "study",	"qr//"

       Numeric functions
	   "abs", "atan2", "cos", "exp", "hex",	"int", "log", "oct", "rand",
	   "sin", "sqrt", "srand"

       Functions for real @ARRAYs
	   "pop", "push", "shift", "splice", "unshift"

       Functions for list data
	   "grep", "join", "map", "qw//", "reverse", "sort", "unpack"

       Functions for real %HASHes
	   "delete", "each", "exists", "keys", "values"

       Input and output	functions
	   "binmode", "close", "closedir", "dbmclose", "dbmopen", "die",
	   "eof", "fileno", "flock", "format", "getc", "print",	"printf",
	   "read", "readdir", "rewinddir", "seek", "seekdir", "select",
	   "syscall", "sysread", "sysseek", "syswrite",	"tell",	"telldir",
	   "truncate", "warn", "write"

       Functions for fixed length data or records
	   "pack", "read", "syscall", "sysread", "syswrite", "unpack", "vec"

       Functions for filehandles, files, or directories
	   "-X", "chdir", "chmod", "chown", "chroot", "fcntl", "glob",
	   "ioctl", "link", "lstat", "mkdir", "open", "opendir", "readlink",
	   "rename", "rmdir", "stat", "symlink", "sysopen", "umask", "unlink",
	   "utime"

       Keywords	related	to the control flow of your Perl program
	   "caller", "continue", "die",	"do", "dump", "eval", "exit", "goto",
	   "last", "next", "redo", "return", "sub", "wantarray"

       Keywords	related	to scoping
	   "caller", "import", "local",	"my", "our", "package",	"use"

       Miscellaneous functions
	   "defined", "dump", "eval", "formline", "local", "my", "our",	"re-
	   set", "scalar", "undef", "wantarray"

       Functions for processes and process groups
	   "alarm", "exec", "fork", "getpgrp", "getppid", "getpriority",
	   "kill", "pipe", "qx//", "setpgrp", "setpriority", "sleep", "sys-
	   tem", "times", "wait", "waitpid"

       Keywords	related	to perl	modules
	   "do", "import", "no", "package", "require", "use"

       Keywords	related	to classes and object-orientation
	   "bless", "dbmclose",	"dbmopen", "package", "ref", "tie", "tied",
	   "untie", "use"

       Low-level socket	functions
	   "accept", "bind", "connect",	"getpeername", "getsockname", "get-
	   sockopt", "listen", "recv", "send", "setsockopt", "shutdown",
	   "socket", "socketpair"

       System V	interprocess communication functions
	   "msgctl", "msgget", "msgrcv", "msgsnd", "semctl", "semget", "se-
	   mop", "shmctl", "shmget", "shmread",	"shmwrite"

       Fetching	user and group info
	   "endgrent", "endhostent", "endnetent", "endpwent", "getgrent",
	   "getgrgid", "getgrnam", "getlogin", "getpwent", "getpwnam", "getp-
	   wuid", "setgrent", "setpwent"

       Fetching	network	info
	   "endprotoent", "endservent",	"gethostbyaddr", "gethostbyname",
	   "gethostent", "getnetbyaddr", "getnetbyname", "getnetent", "getpro-
	   tobyname", "getprotobynumber", "getprotoent", "getservbyname",
	   "getservbyport", "getservent", "sethostent",	"setnetent", "setpro-
	   toent", "setservent"

       Time-related functions
	   "gmtime", "localtime", "time", "times"

       Functions new in	perl5
	   "abs", "bless", "chomp", "chr", "exists", "formline", "glob", "im-
	   port", "lc",	"lcfirst", "lock", "map", "my",	"no", "our", "proto-
	   type", "qr//", "qw//", "qx//", "readline", "readpipe", "ref",
	   "sub"*, "sysopen", "tie", "tied", "uc", "ucfirst", "untie", "use"

	   * - "sub" was a keyword in perl4, but in perl5 it is	an operator,
	   which can be	used in	expressions.

       Functions obsoleted in perl5
	   "dbmclose", "dbmopen"

       Portability

       Perl was	born in	Unix and can therefore access all common Unix system
       calls.  In non-Unix environments, the functionality of some Unix	system
       calls may not be	available, or details of the available functionality
       may differ slightly.  The Perl functions	affected by this are:

       "-X", "binmode",	"chmod", "chown", "chroot", "crypt", "dbmclose", "db-
       mopen", "dump", "endgrent", "endhostent", "endnetent", "endprotoent",
       "endpwent", "endservent", "exec", "fcntl", "flock", "fork", "getgrent",
       "getgrgid", "gethostbyname", "gethostent", "getlogin", "getnetbyaddr",
       "getnetbyname", "getnetent", "getppid", "getpgrp", "getpriority", "get-
       protobynumber", "getprotoent", "getpwent", "getpwnam", "getpwuid",
       "getservbyport",	"getservent", "getsockopt", "glob", "ioctl", "kill",
       "link", "lstat",	"msgctl", "msgget", "msgrcv", "msgsnd",	"open",
       "pipe", "readlink", "rename", "select", "semctl", "semget", "semop",
       "setgrent", "sethostent", "setnetent", "setpgrp", "setpriority",	"set-
       protoent", "setpwent", "setservent", "setsockopt", "shmctl", "shmget",
       "shmread", "shmwrite", "socket",	"socketpair", "stat", "symlink",
       "syscall", "sysopen", "system", "times",	"truncate", "umask", "unlink",
       "utime",	"wait",	"waitpid"

       For more	information about the portability of these functions, see
       perlport	and other available platform-specific documentation.

       Alphabetical Listing of Perl Functions

       -X FILEHANDLE
       -X EXPR
       -X DIRHANDLE
       -X      A file test, where X is one of the letters listed below.	 This
	       unary operator takes one	argument, either a filename, a file-
	       handle, or a dirhandle, and tests the associated	file to	see if
	       something is true about it.  If the argument is omitted,	tests
	       $_, except for "-t", which tests	STDIN.	Unless otherwise docu-
	       mented, it returns 1 for	true and '' for	false, or the unde-
	       fined value if the file doesn't exist.  Despite the funny
	       names, precedence is the	same as	any other named	unary opera-
	       tor.  The operator may be any of:

		   -r  File is readable	by effective uid/gid.
		   -w  File is writable	by effective uid/gid.
		   -x  File is executable by effective uid/gid.
		   -o  File is owned by	effective uid.

		   -R  File is readable	by real	uid/gid.
		   -W  File is writable	by real	uid/gid.
		   -X  File is executable by real uid/gid.
		   -O  File is owned by	real uid.

		   -e  File exists.
		   -z  File has	zero size (is empty).
		   -s  File has	nonzero	size (returns size in bytes).

		   -f  File is a plain file.
		   -d  File is a directory.
		   -l  File is a symbolic link.
		   -p  File is a named pipe (FIFO), or Filehandle is a pipe.
		   -S  File is a socket.
		   -b  File is a block special file.
		   -c  File is a character special file.
		   -t  Filehandle is opened to a tty.

		   -u  File has	setuid bit set.
		   -g  File has	setgid bit set.
		   -k  File has	sticky bit set.

		   -T  File is an ASCII	text file (heuristic guess).
		   -B  File is a "binary" file (opposite of -T).

		   -M  Script start time minus file modification time, in days.
		   -A  Same for	access time.
		   -C  Same for	inode change time (Unix, may differ for	other platforms)

	       Example:

		   while (<>) {
		       chomp;
		       next unless -f $_;      # ignore	specials
		       #...
		   }

	       The interpretation of the file permission operators "-r", "-R",
	       "-w", "-W", "-x", and "-X" is by	default	based solely on	the
	       mode of the file	and the	uids and gids of the user.  There may
	       be other	reasons	you can't actually read, write,	or execute the
	       file: for example network filesystem access controls, ACLs (ac-
	       cess control lists), read-only filesystems, and unrecognized
	       executable formats.  Note that the use of these six specific
	       operators to verify if some operation is	possible is usually a
	       mistake,	because	it may be open to race conditions.

	       Also note that, for the superuser on the	local filesystems, the
	       "-r", "-R", "-w", and "-W" tests	always return 1, and "-x" and
	       "-X" return 1 if	any execute bit	is set in the mode.  Scripts
	       run by the superuser may	thus need to do	a stat() to determine
	       the actual mode of the file, or temporarily set their effective
	       uid to something	else.

	       If you are using	ACLs, there is a pragma	called "filetest" that
	       may produce more	accurate results than the bare stat() mode
	       bits.  When under the "use filetest 'access'" the above-men-
	       tioned filetests	will test whether the permission can (not) be
	       granted using the access() family of system calls.  Also	note
	       that the	"-x" and "-X" may under	this pragma return true	even
	       if there	are no execute permission bits set (nor	any extra exe-
	       cute permission ACLs).  This strangeness	is due to the underly-
	       ing system calls' definitions. Note also	that, due to the im-
	       plementation of "use filetest 'access'",	the "_"	special	file-
	       handle won't cache the results of the file tests	when this
	       pragma is in effect.  Read the documentation for	the "filetest"
	       pragma for more information.

	       Note that "-s/a/b/" does	not do a negated substitution.	Saying
	       "-exp($foo)" still works	as expected, however--only single let-
	       ters following a	minus are interpreted as file tests.

	       The "-T"	and "-B" switches work as follows.  The	first block or
	       so of the file is examined for odd characters such as strange
	       control codes or	characters with	the high bit set.  If too many
	       strange characters (>30%) are found, it's a "-B"	file; other-
	       wise it's a "-T"	file.  Also, any file containing null in the
	       first block is considered a binary file.	 If "-T" or "-B" is
	       used on a filehandle, the current IO buffer is examined rather
	       than the	first block.  Both "-T"	and "-B" return	true on	a null
	       file, or	a file at EOF when testing a filehandle.  Because you
	       have to read a file to do the "-T" test,	on most	occasions you
	       want to use a "-f" against the file first, as in	"next unless
	       -f $file	&& -T $file".

	       If any of the file tests	(or either the "stat" or "lstat" oper-
	       ators) are given	the special filehandle consisting of a soli-
	       tary underline, then the	stat structure of the previous file
	       test (or	stat operator) is used,	saving a system	call.  (This
	       doesn't work with "-t", and you need to remember	that lstat()
	       and "-l"	will leave values in the stat structure	for the	sym-
	       bolic link, not the real	file.)	(Also, if the stat buffer was
	       filled by an "lstat" call, "-T" and "-B"	will reset it with the
	       results of "stat	_").  Example:

		   print "Can do.\n" if	-r $a || -w _ || -x _;

		   stat($filename);
		   print "Readable\n" if -r _;
		   print "Writable\n" if -w _;
		   print "Executable\n"	if -x _;
		   print "Setuid\n" if -u _;
		   print "Setgid\n" if -g _;
		   print "Sticky\n" if -k _;
		   print "Text\n" if -T	_;
		   print "Binary\n" if -B _;

       abs VALUE
       abs     Returns the absolute value of its argument.  If VALUE is	omit-
	       ted, uses $_.

       accept NEWSOCKET,GENERICSOCKET
	       Accepts an incoming socket connect, just	as the accept(2) sys-
	       tem call	does.  Returns the packed address if it	succeeded,
	       false otherwise.	 See the example in "Sockets: Client/Server
	       Communication" in perlipc.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened	file descriptor, as determined
	       by the value of $^F.  See "$^F" in perlvar.

       alarm SECONDS
       alarm   Arranges	to have	a SIGALRM delivered to this process after the
	       specified number	of wallclock seconds has elapsed.  If SECONDS
	       is not specified, the value stored in $_	is used. (On some ma-
	       chines, unfortunately, the elapsed time may be up to one	second
	       less or more than you specified because of how seconds are
	       counted,	and process scheduling may delay the delivery of the
	       signal even further.)

	       Only one	timer may be counting at once.	Each call disables the
	       previous	timer, and an argument of 0 may	be supplied to cancel
	       the previous timer without starting a new one.  The returned
	       value is	the amount of time remaining on	the previous timer.

	       For delays of finer granularity than one	second,	the
	       Time::HiRes module (from	CPAN, and starting from	Perl 5.8 part
	       of the standard distribution) provides ualarm().	 You may also
	       use Perl's four-argument	version	of select() leaving the	first
	       three arguments undefined, or you might be able to use the
	       "syscall" interface to access setitimer(2) if your system sup-
	       ports it. See perlfaq8 for details.

	       It is usually a mistake to intermix "alarm" and "sleep" calls.
	       ("sleep"	may be internally implemented in your system with
	       "alarm")

	       If you want to use "alarm" to time out a	system call you	need
	       to use an "eval"/"die" pair.  You can't rely on the alarm caus-
	       ing the system call to fail with	$! set to "EINTR" because Perl
	       sets up signal handlers to restart system calls on some sys-
	       tems.  Using "eval"/"die" always	works, modulo the caveats
	       given in	"Signals" in perlipc.

		   eval	{
		       local $SIG{ALRM}	= sub {	die "alarm\n" }; # NB: \n required
		       alarm $timeout;
		       $nread =	sysread	SOCKET,	$buffer, $size;
		       alarm 0;
		   };
		   if ($@) {
		       die unless $@ eq	"alarm\n";   # propagate unexpected errors
		       # timed out
		   }
		   else	{
		       # didn't
		   }

	       For more	information see	perlipc.

       atan2 Y,X
	       Returns the arctangent of Y/X in	the range -PI to PI.

	       For the tangent operation, you may use the "Math::Trig::tan"
	       function, or use	the familiar relation:

		   sub tan { sin($_[0])	/ cos($_[0])  }

	       Note that atan2(0, 0) is	not well-defined.

       bind SOCKET,NAME
	       Binds a network address to a socket, just as the	bind system
	       call does.  Returns true	if it succeeded, false otherwise.
	       NAME should be a	packed address of the appropriate type for the
	       socket.	See the	examples in "Sockets: Client/Server Communica-
	       tion" in	perlipc.

       binmode FILEHANDLE, LAYER
       binmode FILEHANDLE
	       Arranges	for FILEHANDLE to be read or written in	"binary" or
	       "text" mode on systems where the	run-time libraries distinguish
	       between binary and text files.  If FILEHANDLE is	an expression,
	       the value is taken as the name of the filehandle.  Returns true
	       on success, otherwise it	returns	"undef"	and sets $! (errno).

	       On some systems (in general, DOS	and Windows-based systems)
	       binmode() is necessary when you're not working with a text
	       file.  For the sake of portability it is	a good idea to always
	       use it when appropriate,	and to never use it when it isn't ap-
	       propriate.  Also, people	can set	their I/O to be	by default
	       UTF-8 encoded Unicode, not bytes.

	       In other	words: regardless of platform, use binmode() on	binary
	       data, like for example images.

	       If LAYER	is present it is a single string, but may contain mul-
	       tiple directives. The directives	alter the behaviour of the
	       file handle.  When LAYER	is present using binmode on a text
	       file makes sense.

	       If LAYER	is omitted or specified	as ":raw" the filehandle is
	       made suitable for passing binary	data. This includes turning
	       off possible CRLF translation and marking it as bytes (as op-
	       posed to	Unicode	characters).  Note that, despite what may be
	       implied in "Programming Perl" (the Camel) or elsewhere, ":raw"
	       is not simply the inverse of ":crlf" -- other layers which
	       would affect the	binary nature of the stream are	also disabled.
	       See PerlIO, perlrun and the discussion about the	PERLIO envi-
	       ronment variable.

	       The ":bytes", ":crlf", and ":utf8", and any other directives of
	       the form	":...",	are called I/O layers.	The "open" pragma can
	       be used to establish default I/O	layers.	 See open.

	       The LAYER parameter of the binmode() function is	described as
	       "DISCIPLINE" in "Programming Perl, 3rd Edition".	 However,
	       since the publishing of this book, by many known	as "Camel
	       III", the consensus of the naming of this functionality has
	       moved from "discipline" to "layer".  All	documentation of this
	       version of Perl therefore refers	to "layers" rather than	to
	       "disciplines".  Now back	to the regularly scheduled documenta-
	       tion...

	       To mark FILEHANDLE as UTF-8, use	":utf8"	or ":encoding(utf8)".
	       ":utf8" just marks the data as UTF-8 without further checking,
	       while ":encoding(utf8)" checks the data for actually being
	       valid UTF-8. More details can be	found in PerlIO::encoding.

	       In general, binmode() should be called after open() but before
	       any I/O is done on the filehandle.  Calling binmode() will nor-
	       mally flush any pending buffered	output data (and perhaps pend-
	       ing input data) on the handle.  An exception to this is the
	       ":encoding" layer that changes the default character encoding
	       of the handle, see open.	 The ":encoding" layer sometimes needs
	       to be called in mid-stream, and it doesn't flush	the stream.
	       The ":encoding" also implicitly pushes on top of	itself the
	       ":utf8" layer because internally	Perl will operate on UTF-8 en-
	       coded Unicode characters.

	       The operating system, device drivers, C libraries, and Perl
	       run-time	system all work	together to let	the programmer treat a
	       single character	("\n") as the line terminator, irrespective of
	       the external representation.  On	many operating systems,	the
	       native text file	representation matches the internal represen-
	       tation, but on some platforms the external representation of
	       "\n" is made up of more than one	character.

	       Mac OS, all variants of Unix, and Stream_LF files on VMS	use a
	       single character	to end each line in the	external representa-
	       tion of text (even though that single character is CARRIAGE RE-
	       TURN on Mac OS and LINE FEED on Unix and	most VMS files). In
	       other systems like OS/2,	DOS and	the various flavors of MS-Win-
	       dows your program sees a	"\n" as	a simple "\cJ",	but what's
	       stored in text files are	the two	characters "\cM\cJ".  That
	       means that, if you don't	use binmode() on these systems,
	       "\cM\cJ"	sequences on disk will be converted to "\n" on input,
	       and any "\n" in your program will be converted back to "\cM\cJ"
	       on output.  This	is what	you want for text files, but it	can be
	       disastrous for binary files.

	       Another consequence of using binmode() (on some systems)	is
	       that special end-of-file	markers	will be	seen as	part of	the
	       data stream.  For systems from the Microsoft family this	means
	       that if your binary data	contains "\cZ",	the I/O	subsystem will
	       regard it as the	end of the file, unless	you use	binmode().

	       binmode() is not	only important for readline() and print() op-
	       erations, but also when using read(), seek(), sysread(),
	       syswrite() and tell() (see perlport for more details).  See the
	       $/ and "$\" variables in	perlvar	for how	to manually set	your
	       input and output	line-termination sequences.

       bless REF,CLASSNAME
       bless REF
	       This function tells the thingy referenced by REF	that it	is now
	       an object in the	CLASSNAME package.  If CLASSNAME is omitted,
	       the current package is used.  Because a "bless" is often	the
	       last thing in a constructor, it returns the reference for con-
	       venience.  Always use the two-argument version if a derived
	       class might inherit the function	doing the blessing.  See perl-
	       toot and	perlobj	for more about the blessing (and blessings) of
	       objects.

	       Consider	always blessing	objects	in CLASSNAMEs that are mixed
	       case.  Namespaces with all lowercase names are considered re-
	       served for Perl pragmata.  Builtin types	have all uppercase
	       names. To prevent confusion, you	may wish to avoid such package
	       names as	well.  Make sure that CLASSNAME	is a true value.

	       See "Perl Modules" in perlmod.

       caller EXPR
       caller  Returns the context of the current subroutine call.  In scalar
	       context,	returns	the caller's package name if there is a
	       caller, that is,	if we're in a subroutine or "eval" or "re-
	       quire", and the undefined value otherwise.  In list context,
	       returns

		   # 0	       1	  2
		   ($package, $filename, $line)	= caller;

	       With EXPR, it returns some extra	information that the debugger
	       uses to print a stack trace.  The value of EXPR indicates how
	       many call frames	to go back before the current one.

		   #  0		1	   2	  3	       4
		   ($package, $filename, $line,	$subroutine, $hasargs,

		   #  5		 6	    7		 8	 9
		   $wantarray, $evaltext, $is_require, $hints, $bitmask) = caller($i);

	       Here $subroutine	may be "(eval)"	if the frame is	not a subrou-
	       tine call, but an "eval".  In such a case additional elements
	       $evaltext and $is_require are set: $is_require is true if the
	       frame is	created	by a "require" or "use"	statement, $evaltext
	       contains	the text of the	"eval EXPR" statement.	In particular,
	       for an "eval BLOCK" statement, $subroutine is "(eval)", but
	       $evaltext is undefined.	(Note also that	each "use" statement
	       creates a "require" frame inside	an "eval EXPR" frame.)	$sub-
	       routine may also	be "(unknown)" if this particular subroutine
	       happens to have been deleted from the symbol table.  $hasargs
	       is true if a new	instance of @_ was set up for the frame.
	       $hints and $bitmask contain pragmatic hints that	the caller was
	       compiled	with.  The $hints and $bitmask values are subject to
	       change between versions of Perl,	and are	not meant for external
	       use.

	       Furthermore, when called	from within the	DB package, caller re-
	       turns more detailed information:	it sets	the list variable
	       @DB::args to be the arguments with which	the subroutine was in-
	       voked.

	       Be aware	that the optimizer might have optimized	call frames
	       away before "caller" had	a chance to get	the information.  That
	       means that caller(N) might not return information about the
	       call frame you expect it	do, for	"N > 1".  In particular,
	       @DB::args might have information	from the previous time
	       "caller"	was called.

       chdir EXPR
       chdir FILEHANDLE
       chdir DIRHANDLE
       chdir   Changes the working directory to	EXPR, if possible. If EXPR is
	       omitted,	changes	to the directory specified by $ENV{HOME}, if
	       set; if not, changes to the directory specified by
	       $ENV{LOGDIR}. (Under VMS, the variable $ENV{SYS$LOGIN} is also
	       checked,	and used if it is set.)	If neither is set, "chdir"
	       does nothing. It	returns	true upon success, false otherwise.
	       See the example under "die".

	       On systems that support fchdir, you might pass a	file handle or
	       directory handle	as argument.  On systems that don't support
	       fchdir, passing handles produces	a fatal	error at run time.

       chmod LIST
	       Changes the permissions of a list of files.  The	first element
	       of the list must	be the numerical mode, which should probably
	       be an octal number, and which definitely	should not be a	string
	       of octal	digits:	0644 is	okay, '0644' is	not.  Returns the num-
	       ber of files successfully changed.  See also "oct", if all you
	       have is a string.

		   $cnt	= chmod	0755, 'foo', 'bar';
		   chmod 0755, @executables;
		   $mode = '0644'; chmod $mode,	'foo';	    # !!! sets mode to
							    # --w----r-T
		   $mode = '0644'; chmod oct($mode), 'foo'; # this is better
		   $mode = 0644;   chmod $mode,	'foo';	    # this is best

	       On systems that support fchmod, you might pass file handles
	       among the files.	 On systems that don't support fchmod, passing
	       file handles produces a fatal error at run time.	  The file
	       handles must be passed as globs or references to	be recognized.
	       Barewords are considered	file names.

		   open(my $fh,	"<", "foo");
		   my $perm = (stat $fh)[2] & 07777;
		   chmod($perm | 0600, $fh);

	       You can also import the symbolic	"S_I*" constants from the Fc-
	       ntl module:

		   use Fcntl ':mode';

		   chmod S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH, @executables;
		   # This is identical to the chmod 0755 of the	above example.

       chomp VARIABLE
       chomp( LIST )
       chomp   This safer version of "chop" removes any	trailing string	that
	       corresponds to the current value	of $/ (also known as $IN-
	       PUT_RECORD_SEPARATOR in the "English" module).  It returns the
	       total number of characters removed from all its arguments.
	       It's often used to remove the newline from the end of an	input
	       record when you're worried that the final record	may be missing
	       its newline.  When in paragraph mode ("$/ = """), it removes
	       all trailing newlines from the string.  When in slurp mode ("$/
	       = undef") or fixed-length record	mode ($/ is a reference	to an
	       integer or the like, see	perlvar) chomp() won't remove any-
	       thing.  If VARIABLE is omitted, it chomps $_.  Example:

		   while (<>) {
		       chomp;  # avoid \n on last field
		       @array =	split(/:/);
		       # ...
		   }

	       If VARIABLE is a	hash, it chomps	the hash's values, but not its
	       keys.

	       You can actually	chomp anything that's an lvalue, including an
	       assignment:

		   chomp($cwd =	`pwd`);
		   chomp($answer = <STDIN>);

	       If you chomp a list, each element is chomped, and the total
	       number of characters removed is returned.

	       Note that parentheses are necessary when	you're chomping	any-
	       thing that is not a simple variable.  This is because "chomp
	       $cwd = `pwd`;" is interpreted as	"(chomp	$cwd) =	`pwd`;",
	       rather than as "chomp( $cwd = `pwd` )" which you	might expect.
	       Similarly, "chomp $a, $b" is interpreted	as "chomp($a), $b"
	       rather than as "chomp($a, $b)".

       chop VARIABLE
       chop( LIST )
       chop    Chops off the last character of a string	and returns the	char-
	       acter chopped.  It is much more efficient than "s/.$//s"	be-
	       cause it	neither	scans nor copies the string.  If VARIABLE is
	       omitted,	chops $_.  If VARIABLE is a hash, it chops the hash's
	       values, but not its keys.

	       You can actually	chop anything that's an	lvalue,	including an
	       assignment.

	       If you chop a list, each	element	is chopped.  Only the value of
	       the last	"chop" is returned.

	       Note that "chop"	returns	the last character.  To	return all but
	       the last	character, use "substr($string,	0, -1)".

	       See also	"chomp".

       chown LIST
	       Changes the owner (and group) of	a list of files.  The first
	       two elements of the list	must be	the numeric uid	and gid, in
	       that order.  A value of -1 in either position is	interpreted by
	       most systems to leave that value	unchanged.  Returns the	number
	       of files	successfully changed.

		   $cnt	= chown	$uid, $gid, 'foo', 'bar';
		   chown $uid, $gid, @filenames;

	       On systems that support fchown, you might pass file handles
	       among the files.	 On systems that don't support fchown, passing
	       file handles produces a fatal error at run time.	 The file han-
	       dles must be passed as globs or references to be	recognized.
	       Barewords are considered	file names.

	       Here's an example that looks up nonnumeric uids in the passwd
	       file:

		   print "User:	";
		   chomp($user = <STDIN>);
		   print "Files: ";
		   chomp($pattern = <STDIN>);

		   ($login,$pass,$uid,$gid) = getpwnam($user)
		       or die "$user not in passwd file";

		   @ary	= glob($pattern);      # expand	filenames
		   chown $uid, $gid, @ary;

	       On most systems,	you are	not allowed to change the ownership of
	       the file	unless you're the superuser, although you should be
	       able to change the group	to any of your secondary groups.  On
	       insecure	systems, these restrictions may	be relaxed, but	this
	       is not a	portable assumption.  On POSIX systems,	you can	detect
	       this condition this way:

		   use POSIX qw(sysconf	_PC_CHOWN_RESTRICTED);
		   $can_chown_giveaway = not sysconf(_PC_CHOWN_RESTRICTED);

       chr NUMBER
       chr     Returns the character represented by that NUMBER	in the charac-
	       ter set.	 For example, "chr(65)"	is "A" in either ASCII or Uni-
	       code, and chr(0x263a) is	a Unicode smiley face.

	       If NUMBER is omitted, uses $_.

	       For the reverse,	use "ord".

	       Note that characters from 128 to	255 (inclusive)	are by default
	       internally not encoded as UTF-8 for backward compatibility rea-
	       sons.

	       See perlunicode for more	about Unicode.

       chroot FILENAME
       chroot  This function works like	the system call	by the same name: it
	       makes the named directory the new root directory	for all	fur-
	       ther pathnames that begin with a	"/" by your process and	all
	       its children.  (It doesn't change your current working direc-
	       tory, which is unaffected.)  For	security reasons, this call is
	       restricted to the superuser.  If	FILENAME is omitted, does a
	       "chroot"	to $_.

       close FILEHANDLE
       close   Closes the file or pipe associated with the file	handle,
	       flushes the IO buffers, and closes the system file descriptor.
	       Returns true if those operations	have succeeded and if no error
	       was reported by any PerlIO layer.  Closes the currently se-
	       lected filehandle if the	argument is omitted.

	       You don't have to close FILEHANDLE if you are immediately going
	       to do another "open" on it, because "open" will close it	for
	       you.  (See "open".)  However, an	explicit "close" on an input
	       file resets the line counter ($.), while	the implicit close
	       done by "open" does not.

	       If the file handle came from a piped open, "close" will addi-
	       tionally	return false if	one of the other system	calls involved
	       fails, or if the	program	exits with non-zero status.  (If the
	       only problem was	that the program exited	non-zero, $! will be
	       set to 0.)  Closing a pipe also waits for the process executing
	       on the pipe to complete,	in case	you want to look at the	output
	       of the pipe afterwards, and implicitly puts the exit status
	       value of	that command into $? and "${^CHILD_ERROR_NATIVE}".

	       Prematurely closing the read end	of a pipe (i.e.	before the
	       process writing to it at	the other end has closed it) will re-
	       sult in a SIGPIPE being delivered to the	writer.	 If the	other
	       end can't handle	that, be sure to read all the data before
	       closing the pipe.

	       Example:

		   open(OUTPUT,	'|sort >foo')  # pipe to sort
		       or die "Can't start sort: $!";
		   #...			       # print stuff to	output
		   close OUTPUT		       # wait for sort to finish
		       or warn $! ? "Error closing sort	pipe: $!"
				  : "Exit status $? from sort";
		   open(INPUT, 'foo')	       # get sort's results
		       or die "Can't open 'foo'	for input: $!";

	       FILEHANDLE may be an expression whose value can be used as an
	       indirect	filehandle, usually the	real filehandle	name.

       closedir	DIRHANDLE
	       Closes a	directory opened by "opendir" and returns the success
	       of that system call.

       connect SOCKET,NAME
	       Attempts	to connect to a	remote socket, just as the connect
	       system call does.  Returns true if it succeeded,	false other-
	       wise.  NAME should be a packed address of the appropriate type
	       for the socket.	See the	examples in "Sockets: Client/Server
	       Communication" in perlipc.

       continue	BLOCK
	       "continue" is actually a	flow control statement rather than a
	       function.  If there is a	"continue" BLOCK attached to a BLOCK
	       (typically in a "while" or "foreach"), it is always executed
	       just before the conditional is about to be evaluated again,
	       just like the third part	of a "for" loop	in C.  Thus it can be
	       used to increment a loop	variable, even when the	loop has been
	       continued via the "next"	statement (which is similar to the C
	       "continue" statement).

	       "last", "next", or "redo" may appear within a "continue"	block.
	       "last" and "redo" will behave as	if they	had been executed
	       within the main block.  So will "next", but since it will exe-
	       cute a "continue" block,	it may be more entertaining.

		   while (EXPR)	{
		       ### redo	always comes here
		       do_something;
		   } continue {
		       ### next	always comes here
		       do_something_else;
		       # then back the top to re-check EXPR
		   }
		   ### last always comes here

	       Omitting	the "continue" section is semantically equivalent to
	       using an	empty one, logically enough.  In that case, "next"
	       goes directly back to check the condition at the	top of the
	       loop.

       cos EXPR
       cos     Returns the cosine of EXPR (expressed in	radians).  If EXPR is
	       omitted,	takes cosine of	$_.

	       For the inverse cosine operation, you may use the
	       "Math::Trig::acos()" function, or use this relation:

		   sub acos { atan2( sqrt(1 - $_[0] * $_[0]), $_[0] ) }

       crypt PLAINTEXT,SALT
	       Creates a digest	string exactly like the	crypt(3) function in
	       the C library (assuming that you	actually have a	version	there
	       that has	not been extirpated as a potential munitions).

	       crypt() is a one-way hash function.  The	PLAINTEXT and SALT is
	       turned into a short string, called a digest, which is returned.
	       The same	PLAINTEXT and SALT will	always return the same string,
	       but there is no (known) way to get the original PLAINTEXT from
	       the hash.  Small	changes	in the PLAINTEXT or SALT will result
	       in large	changes	in the digest.

	       There is	no decrypt function.  This function isn't all that
	       useful for cryptography (for that, look for Crypt modules on
	       your nearby CPAN	mirror)	and the	name "crypt" is	a bit of a
	       misnomer.  Instead it is	primarily used to check	if two pieces
	       of text are the same without having to transmit or store	the
	       text itself.  An	example	is checking if a correct password is
	       given.  The digest of the password is stored, not the password
	       itself.	The user types in a password that is crypt()'d with
	       the same	salt as	the stored digest.  If the two digests match
	       the password is correct.

	       When verifying an existing digest string	you should use the di-
	       gest as the salt	(like "crypt($plain, $digest) eq $digest").
	       The SALT	used to	create the digest is visible as	part of	the
	       digest.	This ensures crypt() will hash the new string with the
	       same salt as the	digest.	 This allows your code to work with
	       the standard crypt and with more	exotic implementations.	 In
	       other words, do not assume anything about the returned string
	       itself, or how many bytes in the	digest matter.

	       Traditionally the result	is a string of 13 bytes: two first
	       bytes of	the salt, followed by 11 bytes from the	set
	       "[./0-9A-Za-z]",	and only the first eight bytes of the digest
	       string mattered,	but alternative	hashing	schemes	(like MD5),
	       higher level security schemes (like C2),	and implementations on
	       non-UNIX	platforms may produce different	strings.

	       When choosing a new salt	create a random	two character string
	       whose characters	come from the set "[./0-9A-Za-z]" (like	"join
	       '', ('.', '/', 0..9, 'A'..'Z', 'a'..'z')[rand 64, rand 64]").
	       This set	of characters is just a	recommendation;	the characters
	       allowed in the salt depend solely on your system's crypt	li-
	       brary, and Perl can't restrict what salts "crypt()" accepts.

	       Here's an example that makes sure that whoever runs this	pro-
	       gram knows their	password:

		   $pwd	= (getpwuid($<))[1];

		   system "stty	-echo";
		   print "Password: ";
		   chomp($word = <STDIN>);
		   print "\n";
		   system "stty	echo";

		   if (crypt($word, $pwd) ne $pwd) {
		       die "Sorry...\n";
		   } else {
		       print "ok\n";
		   }

	       Of course, typing in your own password to whoever asks you for
	       it is unwise.

	       The crypt function is unsuitable	for hashing large quantities
	       of data,	not least of all because you can't get the information
	       back.  Look at the Digest module	for more robust	algorithms.

	       If using	crypt()	on a Unicode string (which potentially has
	       characters with codepoints above	255), Perl tries to make sense
	       of the situation	by trying to downgrade (a copy of the string)
	       the string back to an eight-bit byte string before calling
	       crypt() (on that	copy).	If that	works, good.  If not, crypt()
	       dies with "Wide character in crypt".

       dbmclose	HASH
	       [This function has been largely superseded by the "untie" func-
	       tion.]

	       Breaks the binding between a DBM	file and a hash.

       dbmopen HASH,DBNAME,MASK
	       [This function has been largely superseded by the "tie" func-
	       tion.]

	       This binds a dbm(3), ndbm(3), sdbm(3), gdbm(3), or Berkeley DB
	       file to a hash.	HASH is	the name of the	hash.  (Unlike normal
	       "open", the first argument is not a filehandle, even though it
	       looks like one).	 DBNAME	is the name of the database (without
	       the .dir	or .pag	extension if any).  If the database does not
	       exist, it is created with protection specified by MASK (as mod-
	       ified by	the "umask").  If your system supports only the	older
	       DBM functions, you may perform only one "dbmopen" in your pro-
	       gram.  In older versions	of Perl, if your system	had neither
	       DBM nor ndbm, calling "dbmopen" produced	a fatal	error; it now
	       falls back to sdbm(3).

	       If you don't have write access to the DBM file, you can only
	       read hash variables, not	set them.  If you want to test whether
	       you can write, either use file tests or try setting a dummy
	       hash entry inside an "eval", which will trap the	error.

	       Note that functions such	as "keys" and "values" may return huge
	       lists when used on large	DBM files.  You	may prefer to use the
	       "each" function to iterate over large DBM files.	 Example:

		   # print out history file offsets
		   dbmopen(%HIST,'/usr/lib/news/history',0666);
		   while (($key,$val) =	each %HIST) {
		       print $key, ' = ', unpack('L',$val), "\n";
		   }
		   dbmclose(%HIST);

	       See also	AnyDBM_File for	a more general description of the pros
	       and cons	of the various dbm approaches, as well as DB_File for
	       a particularly rich implementation.

	       You can control which DBM library you use by loading that li-
	       brary before you	call dbmopen():

		   use DB_File;
		   dbmopen(%NS_Hist, "$ENV{HOME}/.netscape/history.db")
		       or die "Can't open netscape history file: $!";

       defined EXPR
       defined Returns a Boolean value telling whether EXPR has	a value	other
	       than the	undefined value	"undef".  If EXPR is not present, $_
	       will be checked.

	       Many operations return "undef" to indicate failure, end of
	       file, system error, uninitialized variable, and other excep-
	       tional conditions.  This	function allows	you to distinguish
	       "undef" from other values.  (A simple Boolean test will not
	       distinguish among "undef", zero,	the empty string, and "0",
	       which are all equally false.)  Note that	since "undef" is a
	       valid scalar, its presence doesn't necessarily indicate an ex-
	       ceptional condition: "pop" returns "undef" when its argument is
	       an empty	array, or when the element to return happens to	be
	       "undef".

	       You may also use	"defined(&func)" to check whether subroutine
	       &func has ever been defined.  The return	value is unaffected by
	       any forward declarations	of &func.  Note	that a subroutine
	       which is	not defined may	still be callable: its package may
	       have an "AUTOLOAD" method that makes it spring into existence
	       the first time that it is called	-- see perlsub.

	       Use of "defined"	on aggregates (hashes and arrays) is depre-
	       cated.  It used to report whether memory	for that aggregate has
	       ever been allocated.  This behavior may disappear in future
	       versions	of Perl.  You should instead use a simple test for
	       size:

		   if (@an_array) { print "has array elements\n" }
		   if (%a_hash)	  { print "has hash members\n"	 }

	       When used on a hash element, it tells you whether the value is
	       defined,	not whether the	key exists in the hash.	 Use "exists"
	       for the latter purpose.

	       Examples:

		   print if defined $switch{'D'};
		   print "$val\n" while	defined($val = pop(@ary));
		   die "Can't readlink $sym: $!"
		       unless defined($value = readlink	$sym);
		   sub foo { defined &$bar ? &$bar(@_) : die "No bar"; }
		   $debugging =	0 unless defined $debugging;

	       Note:  Many folks tend to overuse "defined", and	then are sur-
	       prised to discover that the number 0 and	"" (the	zero-length
	       string) are, in fact, defined values.  For example, if you say

		   "ab"	=~ /a(.*)b/;

	       The pattern match succeeds, and $1 is defined, despite the fact
	       that it matched "nothing".  It didn't really fail to match any-
	       thing.  Rather, it matched something that happened to be	zero
	       characters long.	 This is all very above-board and honest.
	       When a function returns an undefined value, it's	an admission
	       that it couldn't	give you an honest answer.  So you should use
	       "defined" only when you're questioning the integrity of what
	       you're trying to	do.  At	other times, a simple comparison to 0
	       or "" is	what you want.

	       See also	"undef", "exists", "ref".

       delete EXPR
	       Given an	expression that	specifies a hash element, array	ele-
	       ment, hash slice, or array slice, deletes the specified ele-
	       ment(s) from the	hash or	array.	In the case of an array, if
	       the array elements happen to be at the end, the size of the ar-
	       ray will	shrink to the highest element that tests true for ex-
	       ists() (or 0 if no such element exists).

	       Returns a list with the same number of elements as the number
	       of elements for which deletion was attempted.  Each element of
	       that list consists of either the	value of the element deleted,
	       or the undefined	value.	In scalar context, this	means that you
	       get the value of	the last element deleted (or the undefined
	       value if	that element did not exist).

		   %hash = (foo	=> 11, bar => 22, baz => 33);
		   $scalar = delete $hash{foo};		    # $scalar is 11
		   $scalar = delete @hash{qw(foo bar)};	    # $scalar is 22
		   @array  = delete @hash{qw(foo bar baz)}; # @array  is (undef,undef,33)

	       Deleting	from %ENV modifies the environment.  Deleting from a
	       hash tied to a DBM file deletes the entry from the DBM file.
	       Deleting	from a "tie"d hash or array may	not necessarily	return
	       anything.

	       Deleting	an array element effectively returns that position of
	       the array to its	initial, uninitialized state.  Subsequently
	       testing for the same element with exists() will return false.
	       Also, deleting array elements in	the middle of an array will
	       not shift the index of the elements after them down.  Use
	       splice()	for that.  See "exists".

	       The following (inefficiently) deletes all the values of %HASH
	       and @ARRAY:

		   foreach $key	(keys %HASH) {
		       delete $HASH{$key};
		   }

		   foreach $index (0 ..	$#ARRAY) {
		       delete $ARRAY[$index];
		   }

	       And so do these:

		   delete @HASH{keys %HASH};

		   delete @ARRAY[0 .. $#ARRAY];

	       But both	of these are slower than just assigning	the empty list
	       or undefining %HASH or @ARRAY:

		   %HASH = ();	       # completely empty %HASH
		   undef %HASH;	       # forget	%HASH ever existed

		   @ARRAY = ();	       # completely empty @ARRAY
		   undef @ARRAY;       # forget	@ARRAY ever existed

	       Note that the EXPR can be arbitrarily complicated as long as
	       the final operation is a	hash element, array element,  hash
	       slice, or array slice lookup:

		   delete $ref->[$x][$y]{$key};
		   delete @{$ref->[$x][$y]}{$key1, $key2, @morekeys};

		   delete $ref->[$x][$y][$index];
		   delete @{$ref->[$x][$y]}[$index1, $index2, @moreindices];

       die LIST
	       Outside an "eval", prints the value of LIST to "STDERR" and ex-
	       its with	the current value of $!	(errno).  If $!	is 0, exits
	       with the	value of "($? >> 8)" (backtick `command` status).  If
	       "($? >> 8)" is 0, exits with 255.  Inside an "eval()," the er-
	       ror message is stuffed into $@ and the "eval" is	terminated
	       with the	undefined value.  This makes "die" the way to raise an
	       exception.

	       Equivalent examples:

		   die "Can't cd to spool: $!\n" unless	chdir '/usr/spool/news';
		   chdir '/usr/spool/news' or die "Can't cd to spool: $!\n"

	       If the last element of LIST does	not end	in a newline, the cur-
	       rent script line	number and input line number (if any) are also
	       printed,	and a newline is supplied.  Note that the "input line
	       number" (also known as "chunk") is subject to whatever notion
	       of "line" happens to be currently in effect, and	is also	avail-
	       able as the special variable $..	 See "$/" in perlvar and "$."
	       in perlvar.

	       Hint: sometimes appending ", stopped" to	your message will
	       cause it	to make	better sense when the string "at foo line 123"
	       is appended.  Suppose you are running script "canasta".

		   die "/etc/games is no good";
		   die "/etc/games is no good, stopped";

	       produce,	respectively

		   /etc/games is no good at canasta line 123.
		   /etc/games is no good, stopped at canasta line 123.

	       See also	exit(),	warn(),	and the	Carp module.

	       If LIST is empty	and $@ already contains	a value	(typically
	       from a previous eval) that value	is reused after	appending
	       "\t...propagated".  This	is useful for propagating exceptions:

		   eval	{ ... };
		   die unless $@ =~ /Expected exception/;

	       If LIST is empty	and $@ contains	an object reference that has a
	       "PROPAGATE" method, that	method will be called with additional
	       file and	line number parameters.	 The return value replaces the
	       value in	$@.  i.e. as if	"$@ = eval { $@->PROPAGATE(__FILE__,
	       __LINE__) };" were called.

	       If $@ is	empty then the string "Died" is	used.

	       die() can also be called	with a reference argument.  If this
	       happens to be trapped within an eval(), $@ contains the refer-
	       ence.  This behavior permits a more elaborate exception han-
	       dling implementation using objects that maintain	arbitrary
	       state about the nature of the exception.	 Such a	scheme is
	       sometimes preferable to matching	particular string values of $@
	       using regular expressions.  Because $@ is a global variable,
	       and eval() may be used within object implementations, care must
	       be taken	that analyzing the error object	doesn't	replace	the
	       reference in the	global variable.  The easiest solution is to
	       make a local copy of the	reference before doing other manipula-
	       tions.  Here's an example:

		   use Scalar::Util 'blessed';

		   eval	{ ... ;	die Some::Module::Exception->new( FOO => "bar" ) };
		   if (my $ev_err = $@)	{
		       if (blessed($ev_err) && $ev_err->isa("Some::Module::Exception"))	{
			   # handle Some::Module::Exception
		       }
		       else {
			   # handle all	other possible exceptions
		       }
		   }

	       Because perl will stringify uncaught exception messages before
	       displaying them,	you may	want to	overload stringification oper-
	       ations on such custom exception objects.	 See overload for de-
	       tails about that.

	       You can arrange for a callback to be run	just before the	"die"
	       does its	deed, by setting the $SIG{__DIE__} hook.  The associ-
	       ated handler will be called with	the error text and can change
	       the error message, if it	sees fit, by calling "die" again.  See
	       "$SIG{expr}" in perlvar for details on setting %SIG entries,
	       and "eval BLOCK"	for some examples.  Although this feature was
	       to be run only right before your	program	was to exit, this is
	       not currently the case--the $SIG{__DIE__} hook is currently
	       called even inside eval()ed blocks/strings!  If one wants the
	       hook to do nothing in such situations, put

		       die @_ if $^S;

	       as the first line of the	handler	(see "$^S" in perlvar).	 Be-
	       cause this promotes strange action at a distance, this counter-
	       intuitive behavior may be fixed in a future release.

       do BLOCK
	       Not really a function.  Returns the value of the	last command
	       in the sequence of commands indicated by	BLOCK.	When modified
	       by the "while" or "until" loop modifier,	executes the BLOCK
	       once before testing the loop condition. (On other statements
	       the loop	modifiers test the conditional first.)

	       "do BLOCK" does not count as a loop, so the loop	control	state-
	       ments "next", "last", or	"redo" cannot be used to leave or
	       restart the block.  See perlsyn for alternative strategies.

       do SUBROUTINE(LIST)
	       This form of subroutine call is deprecated.  See	perlsub.

       do EXPR Uses the	value of EXPR as a filename and	executes the contents
	       of the file as a	Perl script.

		   do 'stat.pl';

	       is just like

		   eval	`cat stat.pl`;

	       except that it's	more efficient and concise, keeps track	of the
	       current filename	for error messages, searches the @INC directo-
	       ries, and updates %INC if the file is found.  See "Predefined
	       Names" in perlvar for these variables.  It also differs in that
	       code evaluated with "do FILENAME" cannot	see lexicals in	the
	       enclosing scope;	"eval STRING" does.  It's the same, however,
	       in that it does reparse the file	every time you call it,	so you
	       probably	don't want to do this inside a loop.

	       If "do" cannot read the file, it	returns	undef and sets $! to
	       the error.  If "do" can read the	file but cannot	compile	it, it
	       returns undef and sets an error message in $@.	If the file is
	       successfully compiled, "do" returns the value of	the last ex-
	       pression	evaluated.

	       Note that inclusion of library modules is better	done with the
	       "use" and "require" operators, which also do automatic error
	       checking	and raise an exception if there's a problem.

	       You might like to use "do" to read in a program configuration
	       file.  Manual error checking can	be done	this way:

		   # read in config files: system first, then user
		   for $file ("/share/prog/defaults.rc",
			      "$ENV{HOME}/.someprogrc")
		  {
		       unless ($return = do $file) {
			   warn	"couldn't parse	$file: $@" if $@;
			   warn	"couldn't do $file: $!"	   unless defined $return;
			   warn	"couldn't run $file"	   unless $return;
		       }
		   }

       dump LABEL
       dump    This function causes an immediate core dump.  See also the -u
	       command-line switch in perlrun, which does the same thing.
	       Primarily this is so that you can use the undump	program	(not
	       supplied) to turn your core dump	into an	executable binary af-
	       ter having initialized all your variables at the	beginning of
	       the program.  When the new binary is executed it	will begin by
	       executing a "goto LABEL"	(with all the restrictions that	"goto"
	       suffers).  Think	of it as a goto	with an	intervening core dump
	       and reincarnation.  If "LABEL" is omitted, restarts the program
	       from the	top.

	       WARNING:	Any files opened at the	time of	the dump will not be
	       open any	more when the program is reincarnated, with possible
	       resulting confusion on the part of Perl.

	       This function is	now largely obsolete, mostly because it's very
	       hard to convert a core file into	an executable. That's why you
	       should now invoke it as "CORE::dump()", if you don't want to be
	       warned against a	possible typo.

       each HASH
	       When called in list context, returns a 2-element	list consist-
	       ing of the key and value	for the	next element of	a hash,	so
	       that you	can iterate over it.  When called in scalar context,
	       returns only the	key for	the next element in the	hash.

	       Entries are returned in an apparently random order.  The	actual
	       random order is subject to change in future versions of perl,
	       but it is guaranteed to be in the same order as either the
	       "keys" or "values" function would produce on the	same (unmodi-
	       fied) hash.  Since Perl 5.8.2 the ordering can be different
	       even between different runs of Perl for security	reasons	(see
	       "Algorithmic Complexity Attacks"	in perlsec).

	       When the	hash is	entirely read, a null array is returned	in
	       list context (which when	assigned produces a false (0) value),
	       and "undef" in scalar context.  The next	call to	"each" after
	       that will start iterating again.	 There is a single iterator
	       for each	hash, shared by	all "each", "keys", and	"values" func-
	       tion calls in the program; it can be reset by reading all the
	       elements	from the hash, or by evaluating	"keys HASH" or "values
	       HASH".  If you add or delete elements of	a hash while you're
	       iterating over it, you may get entries skipped or duplicated,
	       so don't.  Exception: It	is always safe to delete the item most
	       recently	returned by "each()", which means that the following
	       code will work:

		       while (($key, $value) = each %hash) {
			 print $key, "\n";
			 delete	$hash{$key};   # This is safe
		       }

	       The following prints out	your environment like the printenv(1)
	       program,	only in	a different order:

		   while (($key,$value)	= each %ENV) {
		       print "$key=$value\n";
		   }

	       See also	"keys",	"values" and "sort".

       eof FILEHANDLE
       eof ()
       eof     Returns 1 if the	next read on FILEHANDLE	will return end	of
	       file, or	if FILEHANDLE is not open.  FILEHANDLE may be an ex-
	       pression	whose value gives the real filehandle.	(Note that
	       this function actually reads a character	and then "ungetc"s it,
	       so isn't	very useful in an interactive context.)	 Do not	read
	       from a terminal file (or	call "eof(FILEHANDLE)" on it) after
	       end-of-file is reached.	File types such	as terminals may lose
	       the end-of-file condition if you	do.

	       An "eof"	without	an argument uses the last file read.  Using
	       "eof()" with empty parentheses is very different.  It refers to
	       the pseudo file formed from the files listed on the command
	       line and	accessed via the "<>" operator.	 Since "<>" isn't ex-
	       plicitly	opened,	as a normal filehandle is, an "eof()" before
	       "<>" has	been used will cause @ARGV to be examined to determine
	       if input	is available.	Similarly, an "eof()" after "<>" has
	       returned	end-of-file will assume	you are	processing another
	       @ARGV list, and if you haven't set @ARGV, will read input from
	       "STDIN";	see "I/O Operators" in perlop.

	       In a "while (<>)" loop, "eof" or	"eof(ARGV)" can	be used	to de-
	       tect the	end of each file, "eof()" will only detect the end of
	       the last	file.  Examples:

		   # reset line	numbering on each input	file
		   while (<>) {
		       next if /^\s*#/;	       # skip comments
		       print "$.\t$_";
		   } continue {
		       close ARGV  if eof;     # Not eof()!
		   }

		   # insert dashes just	before last line of last file
		   while (<>) {
		       if (eof()) {	       # check for end of last file
			   print "--------------\n";
		       }
		       print;
		       last if eof();	       # needed	if we're reading from a	terminal
		   }

	       Practical hint: you almost never	need to	use "eof" in Perl, be-
	       cause the input operators typically return "undef" when they
	       run out of data,	or if there was	an error.

       eval EXPR
       eval BLOCK
       eval    In the first form, the return value of EXPR is parsed and exe-
	       cuted as	if it were a little Perl program.  The value of	the
	       expression (which is itself determined within scalar context)
	       is first	parsed,	and if there weren't any errors, executed in
	       the lexical context of the current Perl program,	so that	any
	       variable	settings or subroutine and format definitions remain
	       afterwards.  Note that the value	is parsed every	time the
	       "eval" executes.	 If EXPR is omitted, evaluates $_.  This form
	       is typically used to delay parsing and subsequent execution of
	       the text	of EXPR	until run time.

	       In the second form, the code within the BLOCK is	parsed only
	       once--at	the same time the code surrounding the "eval" itself
	       was parsed--and executed	within the context of the current Perl
	       program.	 This form is typically	used to	trap exceptions	more
	       efficiently than	the first (see below), while also providing
	       the benefit of checking the code	within BLOCK at	compile	time.

	       The final semicolon, if any, may	be omitted from	the value of
	       EXPR or within the BLOCK.

	       In both forms, the value	returned is the	value of the last ex-
	       pression	evaluated inside the mini-program; a return statement
	       may be also used, just as with subroutines.  The	expression
	       providing the return value is evaluated in void,	scalar,	or
	       list context, depending on the context of the "eval" itself.
	       See "wantarray" for more	on how the evaluation context can be
	       determined.

	       If there	is a syntax error or runtime error, or a "die" state-
	       ment is executed, "eval"	returns	an undefined value in scalar
	       context or an empty list	in list	context, and $@	is set to the
	       error message.  If there	was no error, $@ is guaranteed to be a
	       null string.  Beware that using "eval" neither silences perl
	       from printing warnings to STDERR, nor does it stuff the text of
	       warning messages	into $@.  To do	either of those, you have to
	       use the $SIG{__WARN__} facility,	or turn	off warnings inside
	       the BLOCK or EXPR using "no warnings 'all'".  See "warn", perl-
	       var, warnings and perllexwarn.

	       Note that, because "eval" traps otherwise-fatal errors, it is
	       useful for determining whether a	particular feature (such as
	       "socket"	or "symlink") is implemented.  It is also Perl's ex-
	       ception trapping	mechanism, where the die operator is used to
	       raise exceptions.

	       If you want to trap errors when loading an XS module, some
	       problems	with the binary	interface (such	as Perl	version	skew)
	       may be fatal even with "eval" unless $ENV{PERL_DL_NONLAZY} is
	       set. See	perlrun.

	       If the code to be executed doesn't vary,	you may	use the	eval-
	       BLOCK form to trap run-time errors without incurring the	pen-
	       alty of recompiling each	time.  The error, if any, is still re-
	       turned in $@.  Examples:

		   # make divide-by-zero nonfatal
		   eval	{ $answer = $a / $b; };	warn $@	if $@;

		   # same thing, but less efficient
		   eval	'$answer = $a /	$b'; warn $@ if	$@;

		   # a compile-time error
		   eval	{ $answer = };		       # WRONG

		   # a run-time	error
		   eval	'$answer =';   # sets $@

	       Using the "eval{}" form as an exception trap in libraries does
	       have some issues.  Due to the current arguably broken state of
	       "__DIE__" hooks,	you may	wish not to trigger any	"__DIE__"
	       hooks that user code may	have installed.	 You can use the "lo-
	       cal $SIG{__DIE__}" construct for	this purpose, as shown in this
	       example:

		   # a very private exception trap for divide-by-zero
		   eval	{ local	$SIG{'__DIE__'}; $answer = $a /	$b; };
		   warn	$@ if $@;

	       This is especially significant, given that "__DIE__" hooks can
	       call "die" again, which has the effect of changing their	error
	       messages:

		   # __DIE__ hooks may modify error messages
		   {
		      local $SIG{'__DIE__'} =
			     sub { (my $x = $_[0]) =~ s/foo/bar/g; die $x };
		      eval { die "foo lives here" };
		      print $@ if $@;		     # prints "bar lives here"
		   }

	       Because this promotes action at a distance, this	counterintu-
	       itive behavior may be fixed in a	future release.

	       With an "eval", you should be especially	careful	to remember
	       what's being looked at when:

		   eval	$x;	       # CASE 1
		   eval	"$x";	       # CASE 2

		   eval	'$x';	       # CASE 3
		   eval	{ $x };	       # CASE 4

		   eval	"\$$x++";      # CASE 5
		   $$x++;	       # CASE 6

	       Cases 1 and 2 above behave identically: they run	the code con-
	       tained in the variable $x.  (Although case 2 has	misleading
	       double quotes making the	reader wonder what else	might be hap-
	       pening (nothing is).)  Cases 3 and 4 likewise behave in the
	       same way: they run the code '$x', which does nothing but	return
	       the value of $x.	 (Case 4 is preferred for purely visual	rea-
	       sons, but it also has the advantage of compiling	at compile-
	       time instead of at run-time.)  Case 5 is	a place	where normally
	       you would like to use double quotes, except that	in this	par-
	       ticular situation, you can just use symbolic references in-
	       stead, as in case 6.

	       The assignment to $@ occurs before restoration of localised
	       variables, which	means a	temporary is required if you want to
	       mask some but not all errors:

		   # alter $@ on nefarious repugnancy only
		   {
		      my $e;
		      {
			 local $@; # protect existing $@
			 eval {	test_repugnancy() };
			 # $@ =~ /nefarious/ and die $@; # DOES	NOT WORK
			 $@ =~ /nefarious/ and $e = $@;
		      }
		      die $e if	defined	$e
		   }

	       "eval BLOCK" does not count as a	loop, so the loop control
	       statements "next", "last", or "redo" cannot be used to leave or
	       restart the block.

	       Note that as a very special case, an "eval ''" executed within
	       the "DB"	package	doesn't	see the	usual surrounding lexical
	       scope, but rather the scope of the first	non-DB piece of	code
	       that called it. You don't normally need to worry	about this un-
	       less you	are writing a Perl debugger.

       exec LIST
       exec PROGRAM LIST
	       The "exec" function executes a system command and never re-
	       turns-- use "system" instead of "exec" if you want it to	re-
	       turn.  It fails and returns false only if the command does not
	       exist and it is executed	directly instead of via	your system's
	       command shell (see below).

	       Since it's a common mistake to use "exec" instead of "system",
	       Perl warns you if there is a following statement	which isn't
	       "die", "warn", or "exit"	(if "-w" is set	 -  but	you always do
	       that).	If you really want to follow an	"exec" with some other
	       statement, you can use one of these styles to avoid the warn-
	       ing:

		   exec	('foo')	  or print STDERR "couldn't exec foo: $!";
		   { exec ('foo') }; print STDERR "couldn't exec foo: $!";

	       If there	is more	than one argument in LIST, or if LIST is an
	       array with more than one	value, calls execvp(3) with the	argu-
	       ments in	LIST.  If there	is only	one scalar argument or an ar-
	       ray with	one element in it, the argument	is checked for shell
	       metacharacters, and if there are	any, the entire	argument is
	       passed to the system's command shell for	parsing	(this is
	       "/bin/sh	-c" on Unix platforms, but varies on other platforms).
	       If there	are no shell metacharacters in the argument, it	is
	       split into words	and passed directly to "execvp", which is more
	       efficient.  Examples:

		   exec	'/bin/echo', 'Your arguments are: ', @ARGV;
		   exec	"sort $outfile | uniq";

	       If you don't really want	to execute the first argument, but
	       want to lie to the program you are executing about its own
	       name, you can specify the program you actually want to run as
	       an "indirect object" (without a comma) in front of the LIST.
	       (This always forces interpretation of the LIST as a multivalued
	       list, even if there is only a single scalar in the list.)  Ex-
	       ample:

		   $shell = '/bin/csh';
		   exec	$shell '-sh';	       # pretend it's a	login shell

	       or, more	directly,

		   exec	{'/bin/csh'} '-sh';    # pretend it's a	login shell

	       When the	arguments get executed via the system shell, results
	       will be subject to its quirks and capabilities.	See "`STRING`"
	       in perlop for details.

	       Using an	indirect object	with "exec" or "system"	is also	more
	       secure.	This usage (which also works fine with system())
	       forces interpretation of	the arguments as a multivalued list,
	       even if the list	had just one argument.	That way you're	safe
	       from the	shell expanding	wildcards or splitting up words	with
	       whitespace in them.

		   @args = ( "echo surprise" );

		   exec	@args;		     # subject to shell	escapes
					       # if @args == 1
		   exec	{ $args[0] } @args;  # safe even with one-arg list

	       The first version, the one without the indirect object, ran the
	       echo program, passing it	"surprise" an argument.	 The second
	       version didn't--it tried	to run a program literally called
	       "echo surprise",	didn't find it,	and set	$? to a	non-zero value
	       indicating failure.

	       Beginning with v5.6.0, Perl will	attempt	to flush all files
	       opened for output before	the exec, but this may not be sup-
	       ported on some platforms	(see perlport).	 To be safe, you may
	       need to set $| ($AUTOFLUSH in English) or call the "aut-
	       oflush()" method	of "IO::Handle"	on any open handles in order
	       to avoid	lost output.

	       Note that "exec"	will not call your "END" blocks, nor will it
	       call any	"DESTROY" methods in your objects.

       exists EXPR
	       Given an	expression that	specifies a hash element or array ele-
	       ment, returns true if the specified element in the hash or ar-
	       ray has ever been initialized, even if the corresponding	value
	       is undefined.

		   print "Exists\n"    if exists $hash{$key};
		   print "Defined\n"   if defined $hash{$key};
		   print "True\n"      if $hash{$key};

		   print "Exists\n"    if exists $array[$index];
		   print "Defined\n"   if defined $array[$index];
		   print "True\n"      if $array[$index];

	       A hash or array element can be true only	if it's	defined, and
	       defined if it exists, but the reverse doesn't necessarily hold
	       true.

	       Given an	expression that	specifies the name of a	subroutine,
	       returns true if the specified subroutine	has ever been de-
	       clared, even if it is undefined.	 Mentioning a subroutine name
	       for exists or defined does not count as declaring it.  Note
	       that a subroutine which does not	exist may still	be callable:
	       its package may have an "AUTOLOAD" method that makes it spring
	       into existence the first	time that it is	called -- see perlsub.

		   print "Exists\n"    if exists &subroutine;
		   print "Defined\n"   if defined &subroutine;

	       Note that the EXPR can be arbitrarily complicated as long as
	       the final operation is a	hash or	array key lookup or subroutine
	       name:

		   if (exists $ref->{A}->{B}->{$key})  { }
		   if (exists $hash{A}{B}{$key})       { }

		   if (exists $ref->{A}->{B}->[$ix])   { }
		   if (exists $hash{A}{B}[$ix])	       { }

		   if (exists &{$ref->{A}{B}{$key}})   { }

	       Although	the deepest nested array or hash will not spring into
	       existence just because its existence was	tested,	any interven-
	       ing ones	will.  Thus "$ref->{"A"}" and "$ref->{"A"}->{"B"}"
	       will spring into	existence due to the existence test for	the
	       $key element above.  This happens anywhere the arrow operator
	       is used,	including even:

		   undef $ref;
		   if (exists $ref->{"Some key"})      { }
		   print $ref;		   # prints HASH(0x80d3d5c)

	       This surprising autovivification	in what	does not at first--or
	       even second--glance appear to be	an lvalue context may be fixed
	       in a future release.

	       See "Pseudo-hashes: Using an array as a hash" in	perlref	for
	       specifics on how	exists() acts when used	on a pseudo-hash.

	       Use of a	subroutine call, rather	than a subroutine name,	as an
	       argument	to exists() is an error.

		   exists &sub;	       # OK
		   exists &sub();      # Error

       exit EXPR
       exit    Evaluates EXPR and exits	immediately with that value.	Exam-
	       ple:

		   $ans	= <STDIN>;
		   exit	0 if $ans =~ /^[Xx]/;

	       See also	"die".	If EXPR	is omitted, exits with 0 status.  The
	       only universally	recognized values for EXPR are 0 for success
	       and 1 for error;	other values are subject to interpretation de-
	       pending on the environment in which the Perl program is run-
	       ning.  For example, exiting 69 (EX_UNAVAILABLE) from a sendmail
	       incoming-mail filter will cause the mailer to return the	item
	       undelivered, but	that's not true	everywhere.

	       Don't use "exit"	to abort a subroutine if there's any chance
	       that someone might want to trap whatever	error happened.	 Use
	       "die" instead, which can	be trapped by an "eval".

	       The exit() function does	not always exit	immediately.  It calls
	       any defined "END" routines first, but these "END" routines may
	       not themselves abort the	exit.  Likewise	any object destructors
	       that need to be called are called before	the real exit.	If
	       this is a problem, you can call "POSIX:_exit($status)" to avoid
	       END and destructor processing.  See perlmod for details.

       exp EXPR
       exp     Returns e (the natural logarithm	base) to the power of EXPR.
	       If EXPR is omitted, gives "exp($_)".

       fcntl FILEHANDLE,FUNCTION,SCALAR
	       Implements the fcntl(2) function.  You'll probably have to say

		   use Fcntl;

	       first to	get the	correct	constant definitions.  Argument	pro-
	       cessing and value return	works just like	"ioctl"	below.	For
	       example:

		   use Fcntl;
		   fcntl($filehandle, F_GETFL, $packed_return_buffer)
		       or die "can't fcntl F_GETFL: $!";

	       You don't have to check for "defined" on	the return from	"fc-
	       ntl".  Like "ioctl", it maps a 0	return from the	system call
	       into "0 but true" in Perl.  This	string is true in boolean con-
	       text and	0 in numeric context.  It is also exempt from the nor-
	       mal -w warnings on improper numeric conversions.

	       Note that "fcntl" will produce a	fatal error if used on a ma-
	       chine that doesn't implement fcntl(2).  See the Fcntl module or
	       your fcntl(2) manpage to	learn what functions are available on
	       your system.

	       Here's an example of setting a filehandle named "REMOTE"	to be
	       non-blocking at the system level.  You'll have to negotiate $|
	       on your own, though.

		   use Fcntl qw(F_GETFL	F_SETFL	O_NONBLOCK);

		   $flags = fcntl(REMOTE, F_GETFL, 0)
			       or die "Can't get flags for the socket: $!\n";

		   $flags = fcntl(REMOTE, F_SETFL, $flags | O_NONBLOCK)
			       or die "Can't set flags for the socket: $!\n";

       fileno FILEHANDLE
	       Returns the file	descriptor for a filehandle, or	undefined if
	       the filehandle is not open.  This is mainly useful for con-
	       structing bitmaps for "select" and low-level POSIX tty-handling
	       operations.  If FILEHANDLE is an	expression, the	value is taken
	       as an indirect filehandle, generally its	name.

	       You can use this	to find	out whether two	handles	refer to the
	       same underlying descriptor:

		   if (fileno(THIS) == fileno(THAT)) {
		       print "THIS and THAT are	dups\n";
		   }

	       (Filehandles connected to memory	objects	via new	features of
	       "open" may return undefined even	though they are	open.)

       flock FILEHANDLE,OPERATION
	       Calls flock(2), or an emulation of it, on FILEHANDLE.  Returns
	       true for	success, false on failure.  Produces a fatal error if
	       used on a machine that doesn't implement	flock(2), fcntl(2)
	       locking,	or lockf(3).  "flock" is Perl's	portable file locking
	       interface, although it locks only entire	files, not records.

	       Two potentially non-obvious but traditional "flock" semantics
	       are that	it waits indefinitely until the	lock is	granted, and
	       that its	locks merely advisory.	Such discretionary locks are
	       more flexible, but offer	fewer guarantees.  This	means that
	       programs	that do	not also use "flock" may modify	files locked
	       with "flock".  See perlport, your port's	specific documenta-
	       tion, or	your system-specific local manpages for	details.  It's
	       best to assume traditional behavior if you're writing portable
	       programs.  (But if you're not, you should as always feel	per-
	       fectly free to write for	your own system's idiosyncrasies
	       (sometimes called "features").  Slavish adherence to portabil-
	       ity concerns shouldn't get in the way of	your getting your job
	       done.)

	       OPERATION is one	of LOCK_SH, LOCK_EX, or	LOCK_UN, possibly com-
	       bined with LOCK_NB.  These constants are	traditionally valued
	       1, 2, 8 and 4, but you can use the symbolic names if you	import
	       them from the Fcntl module, either individually,	or as a	group
	       using the ':flock' tag.	LOCK_SH	requests a shared lock,
	       LOCK_EX requests	an exclusive lock, and LOCK_UN releases	a pre-
	       viously requested lock.	If LOCK_NB is bitwise-or'ed with
	       LOCK_SH or LOCK_EX then "flock" will return immediately rather
	       than blocking waiting for the lock (check the return status to
	       see if you got it).

	       To avoid	the possibility	of miscoordination, Perl now flushes
	       FILEHANDLE before locking or unlocking it.

	       Note that the emulation built with lockf(3) doesn't provide
	       shared locks, and it requires that FILEHANDLE be	open with
	       write intent.  These are	the semantics that lockf(3) imple-
	       ments.  Most if not all systems implement lockf(3) in terms of
	       fcntl(2)	locking, though, so the	differing semantics shouldn't
	       bite too	many people.

	       Note that the fcntl(2) emulation	of flock(3) requires that
	       FILEHANDLE be open with read intent to use LOCK_SH and requires
	       that it be open with write intent to use	LOCK_EX.

	       Note also that some versions of "flock" cannot lock things over
	       the network; you	would need to use the more system-specific
	       "fcntl" for that.  If you like you can force Perl to ignore
	       your system's flock(2) function,	and so provide its own fc-
	       ntl(2)-based emulation, by passing the switch "-Ud_flock" to
	       the Configure program when you configure	perl.

	       Here's a	mailbox	appender for BSD systems.

		   use Fcntl qw(:flock SEEK_END); # import LOCK_* and SEEK_END constants

		   sub lock {
		       my ($fh)	= @_;
		       flock($fh, LOCK_EX) or die "Cannot lock mailbox - $!\n";

		       # and, in case someone appended while we	were waiting...
		       seek($fh, 0, SEEK_END) or die "Cannot seek - $!\n";
		   }

		   sub unlock {
		       my ($fh)	= @_;
		       flock($fh, LOCK_UN) or die "Cannot unlock mailbox - $!\n";
		   }

		   open(my $mbox, ">>",	"/usr/spool/mail/$ENV{'USER'}")
			   or die "Can't open mailbox: $!";

		   lock($mbox);
		   print $mbox $msg,"\n\n";
		   unlock($mbox);

	       On systems that support a real flock(), locks are inherited
	       across fork() calls, whereas those that must resort to the more
	       capricious fcntl() function lose	the locks, making it harder to
	       write servers.

	       See also	DB_File	for other flock() examples.

       fork    Does a fork(2) system call to create a new process running the
	       same program at the same	point.	It returns the child pid to
	       the parent process, 0 to	the child process, or "undef" if the
	       fork is unsuccessful.  File descriptors (and sometimes locks on
	       those descriptors) are shared, while everything else is copied.
	       On most systems supporting fork(), great	care has gone into
	       making it extremely efficient (for example, using copy-on-write
	       technology on data pages), making it the	dominant paradigm for
	       multitasking over the last few decades.

	       Beginning with v5.6.0, Perl will	attempt	to flush all files
	       opened for output before	forking	the child process, but this
	       may not be supported on some platforms (see perlport).  To be
	       safe, you may need to set $| ($AUTOFLUSH	in English) or call
	       the "autoflush()" method	of "IO::Handle"	on any open handles in
	       order to	avoid duplicate	output.

	       If you "fork" without ever waiting on your children, you	will
	       accumulate zombies.  On some systems, you can avoid this	by
	       setting $SIG{CHLD} to "IGNORE".	See also perlipc for more ex-
	       amples of forking and reaping moribund children.

	       Note that if your forked	child inherits system file descriptors
	       like STDIN and STDOUT that are actually connected by a pipe or
	       socket, even if you exit, then the remote server	(such as, say,
	       a CGI script or a backgrounded job launched from	a remote
	       shell) won't think you're done.	You should reopen those	to
	       /dev/null if it's any issue.

       format  Declare a picture format	for use	by the "write" function.  For
	       example:

		   format Something =
		       Test: @<<<<<<<< @||||| @>>>>>
			     $str,     $%,    '$' . int($num)
		   .

		   $str	= "widget";
		   $num	= $cost/$quantity;
		   $~ =	'Something';
		   write;

	       See perlform for	many details and examples.

       formline	PICTURE,LIST
	       This is an internal function used by "format"s, though you may
	       call it,	too.  It formats (see perlform)	a list of values ac-
	       cording to the contents of PICTURE, placing the output into the
	       format output accumulator, $^A (or $ACCUMULATOR in English).
	       Eventually, when	a "write" is done, the contents	of $^A are
	       written to some filehandle.  You	could also read	$^A and	then
	       set $^A back to "".  Note that a	format typically does one
	       "formline" per line of form, but	the "formline" function	itself
	       doesn't care how	many newlines are embedded in the PICTURE.
	       This means that the "~" and "~~"	tokens will treat the entire
	       PICTURE as a single line.  You may therefore need to use	multi-
	       ple formlines to	implement a single record format, just like
	       the format compiler.

	       Be careful if you put double quotes around the picture, because
	       an "@" character	may be taken to	mean the beginning of an array
	       name.  "formline" always	returns	true.  See perlform for	other
	       examples.

       getc FILEHANDLE
       getc    Returns the next	character from the input file attached to
	       FILEHANDLE, or the undefined value at end of file, or if	there
	       was an error (in	the latter case	$! is set).  If	FILEHANDLE is
	       omitted,	reads from STDIN.  This	is not particularly efficient.
	       However,	it cannot be used by itself to fetch single characters
	       without waiting for the user to hit enter.  For that, try some-
	       thing more like:

		   if ($BSD_STYLE) {
		       system "stty cbreak </dev/tty >/dev/tty 2>&1";
		   }
		   else	{
		       system "stty", '-icanon', 'eol',	"\001";
		   }

		   $key	= getc(STDIN);

		   if ($BSD_STYLE) {
		       system "stty -cbreak </dev/tty >/dev/tty	2>&1";
		   }
		   else	{
		       system "stty", 'icanon',	'eol', '^@'; # ASCII null
		   }
		   print "\n";

	       Determination of	whether	$BSD_STYLE should be set is left as an
	       exercise	to the reader.

	       The "POSIX::getattr" function can do this more portably on sys-
	       tems purporting POSIX compliance.  See also the "Term::ReadKey"
	       module from your	nearest	CPAN site; details on CPAN can be
	       found on	"CPAN" in perlmodlib.

       getlogin
	       This implements the C library function of the same name,	which
	       on most systems returns the current login from /etc/utmp, if
	       any.  If	null, use "getpwuid".

		   $login = getlogin ||	getpwuid($<) ||	"Kilroy";

	       Do not consider "getlogin" for authentication: it is not	as se-
	       cure as "getpwuid".

       getpeername SOCKET
	       Returns the packed sockaddr address of other end	of the SOCKET
	       connection.

		   use Socket;
		   $hersockaddr	   = getpeername(SOCK);
		   ($port, $iaddr) = sockaddr_in($hersockaddr);
		   $herhostname	   = gethostbyaddr($iaddr, AF_INET);
		   $herstraddr	   = inet_ntoa($iaddr);

       getpgrp PID
	       Returns the current process group for the specified PID.	 Use a
	       PID of 0	to get the current process group for the current
	       process.	 Will raise an exception if used on a machine that
	       doesn't implement getpgrp(2).  If PID is	omitted, returns
	       process group of	current	process.  Note that the	POSIX version
	       of "getpgrp" does not accept a PID argument, so only "PID==0"
	       is truly	portable.

       getppid Returns the process id of the parent process.

	       Note for	Linux users: on	Linux, the C functions "getpid()" and
	       "getppid()" return different values from	different threads. In
	       order to	be portable, this behavior is not reflected by the
	       perl-level function "getppid()",	that returns a consistent
	       value across threads. If	you want to call the underlying	"getp-
	       pid()", you may use the CPAN module "Linux::Pid".

       getpriority WHICH,WHO
	       Returns the current priority for	a process, a process group, or
	       a user.	(See getpriority(2).)  Will raise a fatal exception if
	       used on a machine that doesn't implement	getpriority(2).

       getpwnam	NAME
       getgrnam	NAME
       gethostbyname NAME
       getnetbyname NAME
       getprotobyname NAME
       getpwuid	UID
       getgrgid	GID
       getservbyname NAME,PROTO
       gethostbyaddr ADDR,ADDRTYPE
       getnetbyaddr ADDR,ADDRTYPE
       getprotobynumber	NUMBER
       getservbyport PORT,PROTO
       getpwent
       getgrent
       gethostent
       getnetent
       getprotoent
       getservent
       setpwent
       setgrent
       sethostent STAYOPEN
       setnetent STAYOPEN
       setprotoent STAYOPEN
       setservent STAYOPEN
       endpwent
       endgrent
       endhostent
       endnetent
       endprotoent
       endservent
	       These routines perform the same functions as their counterparts
	       in the system library.  In list context,	the return values from
	       the various get routines	are as follows:

		   ($name,$passwd,$uid,$gid,
		      $quota,$comment,$gcos,$dir,$shell,$expire) = getpw*
		   ($name,$passwd,$gid,$members) = getgr*
		   ($name,$aliases,$addrtype,$length,@addrs) = gethost*
		   ($name,$aliases,$addrtype,$net) = getnet*
		   ($name,$aliases,$proto) = getproto*
		   ($name,$aliases,$port,$proto) = getserv*

	       (If the entry doesn't exist you get a null list.)

	       The exact meaning of the	$gcos field varies but it usually con-
	       tains the real name of the user (as opposed to the login	name)
	       and other information pertaining	to the user.  Beware, however,
	       that in many system users are able to change this information
	       and therefore it	cannot be trusted and therefore	the $gcos is
	       tainted (see perlsec).  The $passwd and $shell, user's en-
	       crypted password	and login shell, are also tainted, because of
	       the same	reason.

	       In scalar context, you get the name, unless the function	was a
	       lookup by name, in which	case you get the other thing, whatever
	       it is.  (If the entry doesn't exist you get the undefined
	       value.)	For example:

		   $uid	  = getpwnam($name);
		   $name  = getpwuid($num);
		   $name  = getpwent();
		   $gid	  = getgrnam($name);
		   $name  = getgrgid($num);
		   $name  = getgrent();
		   #etc.

	       In getpw*() the fields $quota, $comment,	and $expire are	spe-
	       cial cases in the sense that in many systems they are unsup-
	       ported.	If the $quota is unsupported, it is an empty scalar.
	       If it is	supported, it usually encodes the disk quota.  If the
	       $comment	field is unsupported, it is an empty scalar.  If it is
	       supported it usually encodes some administrative	comment	about
	       the user.  In some systems the $quota field may be $change or
	       $age, fields that have to do with password aging.  In some sys-
	       tems the	$comment field may be $class.  The $expire field, if
	       present,	encodes	the expiration period of the account or	the
	       password.  For the availability and the exact meaning of	these
	       fields in your system, please consult your getpwnam(3) documen-
	       tation and your pwd.h file.  You	can also find out from within
	       Perl what your $quota and $comment fields mean and whether you
	       have the	$expire	field by using the "Config" module and the
	       values "d_pwquota", "d_pwage", "d_pwchange", "d_pwcomment", and
	       "d_pwexpire".  Shadow password files are	only supported if your
	       vendor has implemented them in the intuitive fashion that call-
	       ing the regular C library routines gets the shadow versions if
	       you're running under privilege or if there exists the shadow(3)
	       functions as found in System V (this includes Solaris and
	       Linux.)	Those systems that implement a proprietary shadow
	       password	facility are unlikely to be supported.

	       The $members value returned by getgr*() is a space separated
	       list of the login names of the members of the group.

	       For the gethost*() functions, if	the "h_errno" variable is sup-
	       ported in C, it will be returned	to you via $? if the function
	       call fails.  The	@addrs value returned by a successful call is
	       a list of the raw addresses returned by the corresponding sys-
	       tem library call.  In the Internet domain, each address is four
	       bytes long and you can unpack it	by saying something like:

		   ($a,$b,$c,$d) = unpack('C4',$addr[0]);

	       The Socket library makes	this slightly easier:

		   use Socket;
		   $iaddr = inet_aton("127.1");	# or whatever address
		   $name  = gethostbyaddr($iaddr, AF_INET);

		   # or	going the other	way
		   $straddr = inet_ntoa($iaddr);

	       In the opposite way, to resolve a hostname to the IP address
	       you can write this:

		   use Socket;
		   $packed_ip =	gethostbyname("www.perl.org");
		   if (defined $packed_ip) {
		       $ip_address = inet_ntoa($packed_ip);
		   }

	       Make sure <gethostbyname()> is called in	SCALAR context and
	       that its	return value is	checked	for definedness.

	       If you get tired	of remembering which element of	the return
	       list contains which return value, by-name interfaces are	pro-
	       vided in	standard modules: "File::stat",	"Net::hostent",
	       "Net::netent", "Net::protoent", "Net::servent", "Time::gmtime",
	       "Time::localtime", and "User::grent".  These override the nor-
	       mal built-ins, supplying	versions that return objects with the
	       appropriate names for each field.  For example:

		  use File::stat;
		  use User::pwent;
		  $is_his = (stat($filename)->uid == pwent($whoever)->uid);

	       Even though it looks like they're the same method calls (uid),
	       they aren't, because a "File::stat" object is different from a
	       "User::pwent" object.

       getsockname SOCKET
	       Returns the packed sockaddr address of this end of the SOCKET
	       connection, in case you don't know the address because you have
	       several different IPs that the connection might have come in
	       on.

		   use Socket;
		   $mysockaddr = getsockname(SOCK);
		   ($port, $myaddr) = sockaddr_in($mysockaddr);
		   printf "Connect to %s [%s]\n",
		      scalar gethostbyaddr($myaddr, AF_INET),
		      inet_ntoa($myaddr);

       getsockopt SOCKET,LEVEL,OPTNAME
	       Queries the option named	OPTNAME	associated with	SOCKET at a
	       given LEVEL.  Options may exist at multiple protocol levels de-
	       pending on the socket type, but at least	the uppermost socket
	       level SOL_SOCKET	(defined in the	"Socket" module) will exist.
	       To query	options	at another level the protocol number of	the
	       appropriate protocol controlling	the option should be supplied.
	       For example, to indicate	that an	option is to be	interpreted by
	       the TCP protocol, LEVEL should be set to	the protocol number of
	       TCP, which you can get using getprotobyname.

	       The call	returns	a packed string	representing the requested
	       socket option, or "undef" if there is an	error (the error rea-
	       son will	be in $!). What	exactly	is in the packed string	de-
	       pends in	the LEVEL and OPTNAME, consult your system documenta-
	       tion for	details. A very	common case however is that the	option
	       is an integer, in which case the	result will be a packed	inte-
	       ger which you can decode	using unpack with the "i" (or "I")
	       format.

	       An example testing if Nagle's algorithm is turned on on a
	       socket:

		   use Socket qw(:all);

		   defined(my $tcp = getprotobyname("tcp"))
		       or die "Could not determine the protocol	number for tcp";
		   # my	$tcp = IPPROTO_TCP; # Alternative
		   my $packed =	getsockopt($socket, $tcp, TCP_NODELAY)
		       or die "Could not query TCP_NODELAY socket option: $!";
		   my $nodelay = unpack("I", $packed);
		   print "Nagle's algorithm is turned ", $nodelay ? "off\n" : "on\n";

       glob EXPR
       glob    In list context,	returns	a (possibly empty) list	of filename
	       expansions on the value of EXPR such as the standard Unix shell
	       /bin/csh	would do. In scalar context, glob iterates through
	       such filename expansions, returning undef when the list is ex-
	       hausted.	This is	the internal function implementing the "<*.c>"
	       operator, but you can use it directly. If EXPR is omitted, $_
	       is used.	 The "<*.c>" operator is discussed in more detail in
	       "I/O Operators" in perlop.

	       Note that "glob"	will split its arguments on whitespace,	treat-
	       ing each	segment	as separate pattern.  As such, "glob('*.c
	       *.h')" would match all files with a .c or .h extension.	The
	       expression "glob('.* *')" would match all files in the current
	       working directory.

	       Beginning with v5.6.0, this operator is implemented using the
	       standard	"File::Glob" extension.	 See File::Glob	for details,
	       including "bsd_glob" which does not treat whitespace as a pat-
	       tern separator.

       gmtime EXPR
       gmtime  Works just like localtime but the returned values are localized
	       for the standard	Greenwich time zone.

	       Note: when called in list context, $isdst, the last value re-
	       turned by gmtime	is always 0.  There is no Daylight Saving Time
	       in GMT.

	       See "gmtime" in perlport	for portability	concerns.

       goto LABEL
       goto EXPR
       goto &NAME
	       The "goto-LABEL"	form finds the statement labeled with LABEL
	       and resumes execution there.  It	may not	be used	to go into any
	       construct that requires initialization, such as a subroutine or
	       a "foreach" loop.  It also can't	be used	to go into a construct
	       that is optimized away, or to get out of	a block	or subroutine
	       given to	"sort".	 It can	be used	to go almost anywhere else
	       within the dynamic scope, including out of subroutines, but
	       it's usually better to use some other construct such as "last"
	       or "die".  The author of	Perl has never felt the	need to	use
	       this form of "goto" (in Perl, that is--C	is another matter).
	       (The difference being that C does not offer named loops com-
	       bined with loop control.	 Perl does, and	this replaces most
	       structured uses of "goto" in other languages.)

	       The "goto-EXPR" form expects a label name, whose	scope will be
	       resolved	dynamically.  This allows for computed "goto"s per
	       FORTRAN,	but isn't necessarily recommended if you're optimizing
	       for maintainability:

		   goto	("FOO",	"BAR", "GLARCH")[$i];

	       The "goto-&NAME"	form is	quite different	from the other forms
	       of "goto".  In fact, it isn't a goto in the normal sense	at
	       all, and	doesn't	have the stigma	associated with	other gotos.
	       Instead,	it exits the current subroutine	(losing	any changes
	       set by local()) and immediately calls in	its place the named
	       subroutine using	the current value of @_.  This is used by "AU-
	       TOLOAD" subroutines that	wish to	load another subroutine	and
	       then pretend that the other subroutine had been called in the
	       first place (except that	any modifications to @_	in the current
	       subroutine are propagated to the	other subroutine.)  After the
	       "goto", not even	"caller" will be able to tell that this	rou-
	       tine was	called first.

	       NAME needn't be the name	of a subroutine; it can	be a scalar
	       variable	containing a code reference, or	a block	that evaluates
	       to a code reference.

       grep BLOCK LIST
       grep EXPR,LIST
	       This is similar in spirit to, but not the same as, grep(1) and
	       its relatives.  In particular, it is not	limited	to using regu-
	       lar expressions.

	       Evaluates the BLOCK or EXPR for each element of LIST (locally
	       setting $_ to each element) and returns the list	value consist-
	       ing of those elements for which the expression evaluated	to
	       true.  In scalar	context, returns the number of times the ex-
	       pression	was true.

		   @foo	= grep(!/^#/, @bar);	# weed out comments

	       or equivalently,

		   @foo	= grep {!/^#/} @bar;	# weed out comments

	       Note that $_ is an alias	to the list value, so it can be	used
	       to modify the elements of the LIST.  While this is useful and
	       supported, it can cause bizarre results if the elements of LIST
	       are not variables.  Similarly, grep returns aliases into	the
	       original	list, much as a	for loop's index variable aliases the
	       list elements.  That is,	modifying an element of	a list re-
	       turned by grep (for example, in a "foreach", "map" or another
	       "grep") actually	modifies the element in	the original list.
	       This is usually something to be avoided when writing clear
	       code.

	       See also	"map" for a list composed of the results of the	BLOCK
	       or EXPR.

       hex EXPR
       hex     Interprets EXPR as a hex	string and returns the corresponding
	       value.  (To convert strings that	might start with either	0,
	       "0x", or	"0b", see "oct".)  If EXPR is omitted, uses $_.

		   print hex '0xAf'; # prints '175'
		   print hex 'aF';   # same

	       Hex strings may only represent integers.	 Strings that would
	       cause integer overflow trigger a	warning.  Leading whitespace
	       is not stripped,	unlike oct(). To present something as hex,
	       look into "printf", "sprintf", or "unpack".

       import LIST
	       There is	no builtin "import" function.  It is just an ordinary
	       method (subroutine) defined (or inherited) by modules that wish
	       to export names to another module.  The "use" function calls
	       the "import" method for the package used.  See also "use",
	       perlmod,	and Exporter.

       index STR,SUBSTR,POSITION
       index STR,SUBSTR
	       The index function searches for one string within another, but
	       without the wildcard-like behavior of a full regular-expression
	       pattern match.  It returns the position of the first occurrence
	       of SUBSTR in STR	at or after POSITION.  If POSITION is omitted,
	       starts searching	from the beginning of the string.  POSITION
	       before the beginning of the string or after its end is treated
	       as if it	were the beginning or the end, respectively.  POSITION
	       and the return value are	based at 0 (or whatever	you've set the
	       $[ variable to--but don't do that).  If the substring is	not
	       found, "index" returns one less than the	base, ordinarily "-1".

       int EXPR
       int     Returns the integer portion of EXPR.  If	EXPR is	omitted, uses
	       $_.  You	should not use this function for rounding: one because
	       it truncates towards 0, and two because machine representations
	       of floating point numbers can sometimes produce counterintu-
	       itive results.  For example, "int(-6.725/0.025)"	produces -268
	       rather than the correct -269; that's because it's really	more
	       like -268.99999999999994315658 instead.	Usually, the
	       "sprintf", "printf", or the "POSIX::floor" and "POSIX::ceil"
	       functions will serve you	better than will int().

       ioctl FILEHANDLE,FUNCTION,SCALAR
	       Implements the ioctl(2) function.  You'll probably first	have
	       to say

		   require "sys/ioctl.ph";     # probably in $Config{archlib}/sys/ioctl.ph

	       to get the correct function definitions.	 If sys/ioctl.ph
	       doesn't exist or	doesn't	have the correct definitions you'll
	       have to roll your own, based on your C header files such	as
	       _sys/ioctl.h_.  (There is a Perl	script called h2ph that	comes
	       with the	Perl kit that may help you in this, but	it's nontriv-
	       ial.)  SCALAR will be read and/or written depending on the
	       FUNCTION--a pointer to the string value of SCALAR will be
	       passed as the third argument of the actual "ioctl" call.	 (If
	       SCALAR has no string value but does have	a numeric value, that
	       value will be passed rather than	a pointer to the string	value.
	       To guarantee this to be true, add a 0 to	the scalar before us-
	       ing it.)	 The "pack" and	"unpack" functions may be needed to
	       manipulate the values of	structures used	by "ioctl".

	       The return value	of "ioctl" (and	"fcntl") is as follows:

		       if OS returns:	       then Perl returns:
			   -1			 undefined value
			    0		       string "0 but true"
		       anything	else		   that	number

	       Thus Perl returns true on success and false on failure, yet you
	       can still easily	determine the actual value returned by the op-
	       erating system:

		   $retval = ioctl(...)	|| -1;
		   printf "System returned %d\n", $retval;

	       The special string "0 but true" is exempt from -w complaints
	       about improper numeric conversions.

       join EXPR,LIST
	       Joins the separate strings of LIST into a single	string with
	       fields separated	by the value of	EXPR, and returns that new
	       string.	Example:

		   $rec	= join(':', $login,$passwd,$uid,$gid,$gcos,$home,$shell);

	       Beware that unlike "split", "join" doesn't take a pattern as
	       its first argument.  Compare "split".

       keys HASH
	       Returns a list consisting of all	the keys of the	named hash.
	       (In scalar context, returns the number of keys.)

	       The keys	are returned in	an apparently random order.  The ac-
	       tual random order is subject to change in future	versions of
	       perl, but it is guaranteed to be	the same order as either the
	       "values"	or "each" function produces (given that	the hash has
	       not been	modified).  Since Perl 5.8.1 the ordering is different
	       even between different runs of Perl for security	reasons	(see
	       "Algorithmic Complexity Attacks"	in perlsec).

	       As a side effect, calling keys()	resets the HASH's internal it-
	       erator (see "each").  In	particular, calling keys() in void
	       context resets the iterator with	no other overhead.

	       Here is yet another way to print	your environment:

		   @keys = keys	%ENV;
		   @values = values %ENV;
		   while (@keys) {
		       print pop(@keys), '=', pop(@values), "\n";
		   }

	       or how about sorted by key:

		   foreach $key	(sort(keys %ENV)) {
		       print $key, '=',	$ENV{$key}, "\n";
		   }

	       The returned values are copies of the original keys in the
	       hash, so	modifying them will not	affect the original hash.
	       Compare "values".

	       To sort a hash by value,	you'll need to use a "sort" function.
	       Here's a	descending numeric sort	of a hash by its values:

		   foreach $key	(sort {	$hash{$b} <=> $hash{$a}	} keys %hash) {
		       printf "%4d %s\n", $hash{$key}, $key;
		   }

	       As an lvalue "keys" allows you to increase the number of	hash
	       buckets allocated for the given hash.  This can gain you	a mea-
	       sure of efficiency if you know the hash is going	to get big.
	       (This is	similar	to pre-extending an array by assigning a
	       larger number to	$#array.)  If you say

		   keys	%hash =	200;

	       then %hash will have at least 200 buckets allocated for it--256
	       of them,	in fact, since it rounds up to the next	power of two.
	       These buckets will be retained even if you do "%hash = ()", use
	       "undef %hash" if	you want to free the storage while %hash is
	       still in	scope.	You can't shrink the number of buckets allo-
	       cated for the hash using	"keys" in this way (but	you needn't
	       worry about doing this by accident, as trying has no effect).

	       See also	"each",	"values" and "sort".

       kill SIGNAL, LIST
	       Sends a signal to a list	of processes.  Returns the number of
	       processes successfully signaled (which is not necessarily the
	       same as the number actually killed).

		   $cnt	= kill 1, $child1, $child2;
		   kill	9, @goners;

	       If SIGNAL is zero, no signal is sent to the process, but	the
	       kill(2) system call will	check whether it's possible to send a
	       signal to it (that means, to be brief, that the process is
	       owned by	the same user, or we are the super-user).  This	is a
	       useful way to check that	a child	process	is alive (even if only
	       as a zombie) and	hasn't changed its UID.	 See perlport for
	       notes on	the portability	of this	construct.

	       Unlike in the shell, if SIGNAL is negative, it kills process
	       groups instead of processes.  (On System	V, a negative PROCESS
	       number will also	kill process groups, but that's	not portable.)
	       That means you usually want to use positive not negative	sig-
	       nals.  You may also use a signal	name in	quotes.

	       See "Signals" in	perlipc	for more details.

       last LABEL
       last    The "last" command is like the "break" statement	in C (as used
	       in loops); it immediately exits the loop	in question.  If the
	       LABEL is	omitted, the command refers to the innermost enclosing
	       loop.  The "continue" block, if any, is not executed:

		   LINE: while (<STDIN>) {
		       last LINE if /^$/;      # exit when done	with header
		       #...
		   }

	       "last" cannot be	used to	exit a block which returns a value
	       such as "eval {}", "sub {}" or "do {}", and should not be used
	       to exit a grep()	or map() operation.

	       Note that a block by itself is semantically identical to	a loop
	       that executes once.  Thus "last"	can be used to effect an early
	       exit out	of such	a block.

	       See also	"continue" for an illustration of how "last", "next",
	       and "redo" work.

       lc EXPR
       lc      Returns a lowercased version of EXPR.  This is the internal
	       function	implementing the "\L" escape in	double-quoted strings.
	       Respects	current	LC_CTYPE locale	if "use	locale"	in force.  See
	       perllocale and perlunicode for more details about locale	and
	       Unicode support.

	       If EXPR is omitted, uses	$_.

       lcfirst EXPR
       lcfirst Returns the value of EXPR with the first	character lowercased.
	       This is the internal function implementing the "\l" escape in
	       double-quoted strings.  Respects	current	LC_CTYPE locale	if
	       "use locale" in force.  See perllocale and perlunicode for more
	       details about locale and	Unicode	support.

	       If EXPR is omitted, uses	$_.

       length EXPR
       length  Returns the length in characters	of the value of	EXPR.  If EXPR
	       is omitted, returns length of $_.  Note that this cannot	be
	       used on an entire array or hash to find out how many elements
	       these have.  For	that, use "scalar @array" and "scalar keys
	       %hash" respectively.

	       Note the	characters: if the EXPR	is in Unicode, you will	get
	       the number of characters, not the number	of bytes.  To get the
	       length of the internal string in	bytes, use
	       "bytes::length(EXPR)", see bytes.  Note that the	internal en-
	       coding is variable, and the number of bytes usually meaning-
	       less.  To get the number	of bytes that the string would have
	       when encoded as UTF-8, use "length(Encoding::en-
	       code_utf8(EXPR))".

       link OLDFILE,NEWFILE
	       Creates a new filename linked to	the old	filename.  Returns
	       true for	success, false otherwise.

       listen SOCKET,QUEUESIZE
	       Does the	same thing that	the listen system call does.  Returns
	       true if it succeeded, false otherwise.  See the example in
	       "Sockets: Client/Server Communication" in perlipc.

       local EXPR
	       You really probably want	to be using "my" instead, because "lo-
	       cal" isn't what most people think of as "local".	 See "Private
	       Variables via my()" in perlsub for details.

	       A local modifies	the listed variables to	be local to the	en-
	       closing block, file, or eval.  If more than one value is
	       listed, the list	must be	placed in parentheses.	See "Temporary
	       Values via local()" in perlsub for details, including issues
	       with tied arrays	and hashes.

       localtime EXPR
       localtime
	       Converts	a time as returned by the time function	to a 9-element
	       list with the time analyzed for the local time zone.  Typically
	       used as follows:

		   #  0	   1	2     3	    4	 5     6     7	   8
		   ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
							       localtime(time);

	       All list	elements are numeric, and come straight	out of the C
	       `struct tm'.  $sec, $min, and $hour are the seconds, minutes,
	       and hours of the	specified time.

	       $mday is	the day	of the month, and $mon is the month itself, in
	       the range 0..11 with 0 indicating January and 11	indicating De-
	       cember.	This makes it easy to get a month name from a list:

		   my @abbr = qw( Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec );
		   print "$abbr[$mon] $mday";
		   # $mon=9, $mday=18 gives "Oct 18"

	       $year is	the number of years since 1900,	not just the last two
	       digits of the year.  That is, $year is 123 in year 2023.	 The
	       proper way to get a complete 4-digit year is simply:

		   $year += 1900;

	       Otherwise you create non-Y2K-compliant programs--and you
	       wouldn't	want to	do that, would you?

	       To get the last two digits of the year (e.g., '01' in 2001) do:

		   $year = sprintf("%02d", $year % 100);

	       $wday is	the day	of the week, with 0 indicating Sunday and 3
	       indicating Wednesday.  $yday is the day of the year, in the
	       range 0..364 (or	0..365 in leap years.)

	       $isdst is true if the specified time occurs during Daylight
	       Saving Time, false otherwise.

	       If EXPR is omitted, "localtime()" uses the current time (as re-
	       turned by time(3)).

	       In scalar context, "localtime()"	returns	the ctime(3) value:

		   $now_string = localtime;  # e.g., "Thu Oct 13 04:54:34 1994"

	       This scalar value is not	locale dependent but is	a Perl
	       builtin.	For GMT	instead	of local time use the "gmtime"
	       builtin.	See also the "Time::Local" module (to convert the sec-
	       ond, minutes, hours, ...	back to	the integer value returned by
	       time()),	and the	POSIX module's strftime(3) and mktime(3) func-
	       tions.

	       To get somewhat similar but locale dependent date strings, set
	       up your locale environment variables appropriately (please see
	       perllocale) and try for example:

		   use POSIX qw(strftime);
		   $now_string = strftime "%a %b %e %H:%M:%S %Y", localtime;
		   # or	for GMT	formatted appropriately	for your locale:
		   $now_string = strftime "%a %b %e %H:%M:%S %Y", gmtime;

	       Note that the %a	and %b,	the short forms	of the day of the week
	       and the month of	the year, may not necessarily be three charac-
	       ters wide.

	       See "localtime" in perlport for portability concerns.

	       The Time::gmtime	and Time::localtime modules provides a conve-
	       nient, by-name access mechanism to the gmtime() and localtime()
	       functions, respectively.

	       For a comprehensive date	and time representation	look at	the
	       DateTime	module on CPAN.

       lock THING
	       This function places an advisory	lock on	a shared variable, or
	       referenced object contained in THING until the lock goes	out of
	       scope.

	       lock() is a "weak keyword" : this means that if you've defined
	       a function by this name (before any calls to it), that function
	       will be called instead. (However, if you've said	"use threads",
	       lock() is always	a keyword.) See	threads.

       log EXPR
       log     Returns the natural logarithm (base e) of EXPR.	If EXPR	is
	       omitted,	returns	log of $_.  To get the log of another base,
	       use basic algebra: The base-N log of a number is	equal to the
	       natural log of that number divided by the natural log of	N.
	       For example:

		   sub log10 {
		       my $n = shift;
		       return log($n)/log(10);
		   }

	       See also	"exp" for the inverse operation.

       lstat EXPR
       lstat   Does the	same thing as the "stat" function (including setting
	       the special "_" filehandle) but stats a symbolic	link instead
	       of the file the symbolic	link points to.	 If symbolic links are
	       unimplemented on	your system, a normal "stat" is	done.  For
	       much more detailed information, please see the documentation
	       for "stat".

	       If EXPR is omitted, stats $_.

       m//     The match operator.  See	perlop.

       map BLOCK LIST
       map EXPR,LIST
	       Evaluates the BLOCK or EXPR for each element of LIST (locally
	       setting $_ to each element) and returns the list	value composed
	       of the results of each such evaluation.	In scalar context, re-
	       turns the total number of elements so generated.	 Evaluates
	       BLOCK or	EXPR in	list context, so each element of LIST may pro-
	       duce zero, one, or more elements	in the returned	value.

		   @chars = map(chr, @nums);

	       translates a list of numbers to the corresponding characters.
	       And

		   %hash = map { get_a_key_for($_) => $_ } @array;

	       is just a funny way to write

		   %hash = ();
		   foreach (@array) {
		       $hash{get_a_key_for($_)}	= $_;
		   }

	       Note that $_ is an alias	to the list value, so it can be	used
	       to modify the elements of the LIST.  While this is useful and
	       supported, it can cause bizarre results if the elements of LIST
	       are not variables.  Using a regular "foreach" loop for this
	       purpose would be	clearer	in most	cases.	See also "grep"	for an
	       array composed of those items of	the original list for which
	       the BLOCK or EXPR evaluates to true.

	       "{" starts both hash references and blocks, so "map { ..."
	       could be	either the start of map	BLOCK LIST or map EXPR,	LIST.
	       Because perl doesn't look ahead for the closing "}" it has to
	       take a guess at which its dealing with based what it finds just
	       after the "{". Usually it gets it right,	but if it doesn't it
	       won't realize something is wrong	until it gets to the "}" and
	       encounters the missing (or unexpected) comma. The syntax	error
	       will be reported	close to the "}" but you'll need to change
	       something near the "{" such as using a unary "+"	to give	perl
	       some help:

		   %hash = map {  "\L$_", 1  } @array  # perl guesses EXPR.  wrong
		   %hash = map { +"\L$_", 1  } @array  # perl guesses BLOCK. right
		   %hash = map { ("\L$_", 1) } @array  # this also works
		   %hash = map {  lc($_), 1  } @array  # as does this.
		   %hash = map +( lc($_), 1 ), @array  # this is EXPR and works!

		   %hash = map	( lc($_), 1 ), @array  # evaluates to (1, @array)

	       or to force an anon hash	constructor use	"+{":

		  @hashes = map	+{ lc($_), 1 },	@array # EXPR, so needs	, at end

	       and you get list	of anonymous hashes each with only 1 entry.

       mkdir FILENAME,MASK
       mkdir FILENAME
	       Creates the directory specified by FILENAME, with permissions
	       specified by MASK (as modified by "umask").  If it succeeds it
	       returns true, otherwise it returns false	and sets $! (errno).
	       If omitted, MASK	defaults to 0777.

	       In general, it is better	to create directories with permissive
	       MASK, and let the user modify that with their "umask", than it
	       is to supply a restrictive MASK and give	the user no way	to be
	       more permissive.	 The exceptions	to this	rule are when the file
	       or directory should be kept private (mail files,	for instance).
	       The perlfunc(1) entry on	"umask"	discusses the choice of	MASK
	       in more detail.

	       Note that according to the POSIX	1003.1-1996 the	FILENAME may
	       have any	number of trailing slashes.  Some operating and
	       filesystems do not get this right, so Perl automatically	re-
	       moves all trailing slashes to keep everyone happy.

	       In order	to recursively create a	directory structure look at
	       the "mkpath" function of	the File::Path module.

       msgctl ID,CMD,ARG
	       Calls the System	V IPC function msgctl(2).  You'll probably
	       have to say

		   use IPC::SysV;

	       first to	get the	correct	constant definitions.  If CMD is
	       "IPC_STAT", then	ARG must be a variable that will hold the re-
	       turned "msqid_ds" structure.  Returns like "ioctl": the unde-
	       fined value for error, "0 but true" for zero, or	the actual re-
	       turn value otherwise.  See also "SysV IPC" in perlipc,
	       "IPC::SysV", and	"IPC::Semaphore" documentation.

       msgget KEY,FLAGS
	       Calls the System	V IPC function msgget(2).  Returns the message
	       queue id, or the	undefined value	if there is an error.  See
	       also "SysV IPC" in perlipc and "IPC::SysV" and "IPC::Msg" docu-
	       mentation.

       msgrcv ID,VAR,SIZE,TYPE,FLAGS
	       Calls the System	V IPC function msgrcv to receive a message
	       from message queue ID into variable VAR with a maximum message
	       size of SIZE.  Note that	when a message is received, the	mes-
	       sage type as a native long integer will be the first thing in
	       VAR, followed by	the actual message.  This packing may be
	       opened with "unpack("l! a*")".  Taints the variable.  Returns
	       true if successful, or false if there is	an error.  See also
	       "SysV IPC" in perlipc, "IPC::SysV", and "IPC::SysV::Msg"	docu-
	       mentation.

       msgsnd ID,MSG,FLAGS
	       Calls the System	V IPC function msgsnd to send the message MSG
	       to the message queue ID.	 MSG must begin	with the native	long
	       integer message type, and be followed by	the length of the ac-
	       tual message, and finally the message itself.  This kind	of
	       packing can be achieved with "pack("l! a*", $type, $message)".
	       Returns true if successful, or false if there is	an error.  See
	       also "IPC::SysV"	and "IPC::SysV::Msg" documentation.

       my EXPR
       my TYPE EXPR
       my EXPR : ATTRS
       my TYPE EXPR : ATTRS
	       A "my" declares the listed variables to be local	(lexically) to
	       the enclosing block, file, or "eval".  If more than one value
	       is listed, the list must	be placed in parentheses.

	       The exact semantics and interface of TYPE and ATTRS are still
	       evolving.  TYPE is currently bound to the use of	"fields"
	       pragma, and attributes are handled using	the "attributes"
	       pragma, or starting from	Perl 5.8.0 also	via the	"Attri-
	       bute::Handlers" module.	See "Private Variables via my()" in
	       perlsub for details, and	fields,	attributes, and	Attri-
	       bute::Handlers.

       next LABEL
       next    The "next" command is like the "continue" statement in C; it
	       starts the next iteration of the	loop:

		   LINE: while (<STDIN>) {
		       next LINE if /^#/;      # discard comments
		       #...
		   }

	       Note that if there were a "continue" block on the above,	it
	       would get executed even on discarded lines.  If the LABEL is
	       omitted,	the command refers to the innermost enclosing loop.

	       "next" cannot be	used to	exit a block which returns a value
	       such as "eval {}", "sub {}" or "do {}", and should not be used
	       to exit a grep()	or map() operation.

	       Note that a block by itself is semantically identical to	a loop
	       that executes once.  Thus "next"	will exit such a block early.

	       See also	"continue" for an illustration of how "last", "next",
	       and "redo" work.

       no Module VERSION LIST
       no Module VERSION
       no Module LIST
       no Module
	       See the "use" function, which "no" is the opposite of.

       oct EXPR
       oct     Interprets EXPR as an octal string and returns the correspond-
	       ing value.  (If EXPR happens to start off with "0x", interprets
	       it as a hex string.  If EXPR starts off with "0b", it is	inter-
	       preted as a binary string.  Leading whitespace is ignored in
	       all three cases.)  The following	will handle decimal, binary,
	       octal, and hex in the standard Perl or C	notation:

		   $val	= oct($val) if $val =~ /^0/;

	       If EXPR is omitted, uses	$_.   To go the	other way (produce a
	       number in octal), use sprintf() or printf():

		   $perms = (stat("filename"))[2] & 07777;
		   $oct_perms =	sprintf	"%lo", $perms;

	       The oct() function is commonly used when	a string such as 644
	       needs to	be converted into a file mode, for example. (Although
	       perl will automatically convert strings into numbers as needed,
	       this automatic conversion assumes base 10.)

       open FILEHANDLE,EXPR
       open FILEHANDLE,MODE,EXPR
       open FILEHANDLE,MODE,EXPR,LIST
       open FILEHANDLE,MODE,REFERENCE
       open FILEHANDLE
	       Opens the file whose filename is	given by EXPR, and associates
	       it with FILEHANDLE.

	       Simple examples to open a file for reading:

		   open(my $fh,	'<', "input.txt") or die $!;

	       and for writing:

		   open(my $fh,	'>', "output.txt") or die $!;

	       (The following is a comprehensive reference to open(): for a
	       gentler introduction you	may consider perlopentut.)

	       If FILEHANDLE is	an undefined scalar variable (or array or hash
	       element)	the variable is	assigned a reference to	a new anony-
	       mous filehandle,	otherwise if FILEHANDLE	is an expression, its
	       value is	used as	the name of the	real filehandle	wanted.	 (This
	       is considered a symbolic	reference, so "use strict 'refs'"
	       should not be in	effect.)

	       If EXPR is omitted, the scalar variable of the same name	as the
	       FILEHANDLE contains the filename.  (Note	that lexical vari-
	       ables--those declared with "my"--will not work for this pur-
	       pose; so	if you're using	"my", specify EXPR in your call	to
	       open.)

	       If three	or more	arguments are specified	then the mode of open-
	       ing and the file	name are separate. If MODE is '<' or nothing,
	       the file	is opened for input.  If MODE is '>', the file is
	       truncated and opened for	output,	being created if necessary.
	       If MODE is '>>',	the file is opened for appending, again	being
	       created if necessary.

	       You can put a '+' in front of the '>' or	'<' to indicate	that
	       you want	both read and write access to the file;	thus '+<' is
	       almost always preferred for read/write updates--the '+>'	mode
	       would clobber the file first.  You can't	usually	use either
	       read-write mode for updating textfiles, since they have vari-
	       able length records.  See the -i	switch in perlrun for a	better
	       approach.  The file is created with permissions of 0666 modi-
	       fied by the process' "umask" value.

	       These various prefixes correspond to the	fopen(3) modes of 'r',
	       'r+', 'w', 'w+',	'a', and 'a+'.

	       In the 2-arguments (and 1-argument) form	of the call the	mode
	       and filename should be concatenated (in this order), possibly
	       separated by spaces.  It	is possible to omit the	mode in	these
	       forms if	the mode is '<'.

	       If the filename begins with '|',	the filename is	interpreted as
	       a command to which output is to be piped, and if	the filename
	       ends with a '|',	the filename is	interpreted as a command which
	       pipes output to us.  See	"Using open() for IPC" in perlipc for
	       more examples of	this.  (You are	not allowed to "open" to a
	       command that pipes both in and out, but see IPC::Open2,
	       IPC::Open3, and "Bidirectional Communication with Another
	       Process"	in perlipc for alternatives.)

	       For three or more arguments if MODE is '|-', the	filename is
	       interpreted as a	command	to which output	is to be piped,	and if
	       MODE is '-|', the filename is interpreted as a command which
	       pipes output to us.  In the 2-arguments (and 1-argument)	form
	       one should replace dash ('-') with the command.	See "Using
	       open() for IPC" in perlipc for more examples of this.  (You are
	       not allowed to "open" to	a command that pipes both in and out,
	       but see IPC::Open2, IPC::Open3, and "Bidirectional Communica-
	       tion" in	perlipc	for alternatives.)

	       In the three-or-more argument form of pipe opens, if LIST is
	       specified (extra	arguments after	the command name) then LIST
	       becomes arguments to the	command	invoked	if the platform	sup-
	       ports it.  The meaning of "open"	with more than three arguments
	       for non-pipe modes is not yet specified.	Experimental "layers"
	       may give	extra LIST arguments meaning.

	       In the 2-arguments (and 1-argument) form	opening	'-' opens
	       STDIN and opening '>-' opens STDOUT.

	       You may use the three-argument form of open to specify IO "lay-
	       ers" (sometimes also referred to	as "disciplines") to be	ap-
	       plied to	the handle that	affect how the input and output	are
	       processed (see open and PerlIO for more details). For example

		 open(my $fh, "<:encoding(UTF-8)", "file")

	       will open the UTF-8 encoded file	containing Unicode characters,
	       see perluniintro. Note that if layers are specified in the
	       three-arg form then default layers stored in ${^OPEN} (see per-
	       lvar; usually set by the	open pragma or the switch -CioD) are
	       ignored.

	       Open returns nonzero upon success, the undefined	value other-
	       wise.  If the "open" involved a pipe, the return	value happens
	       to be the pid of	the subprocess.

	       If you're running Perl on a system that distinguishes between
	       text files and binary files, then you should check out "bin-
	       mode" for tips for dealing with this.  The key distinction be-
	       tween systems that need "binmode" and those that	don't is their
	       text file formats.  Systems like	Unix, Mac OS, and Plan 9,
	       which delimit lines with	a single character, and	which encode
	       that character in C as "\n", do not need	"binmode".  The	rest
	       need it.

	       When opening a file, it's usually a bad idea to continue	normal
	       execution if the	request	failed,	so "open" is frequently	used
	       in connection with "die".  Even if "die"	won't do what you want
	       (say, in	a CGI script, where you	want to	make a nicely format-
	       ted error message (but there are	modules	that can help with
	       that problem)) you should always	check the return value from
	       opening a file.	The infrequent exception is when working with
	       an unopened filehandle is actually what you want	to do.

	       As a special case the 3-arg form	with a read/write mode and the
	       third argument being "undef":

		   open(my $tmp, "+>", undef) or die ...

	       opens a filehandle to an	anonymous temporary file.  Also	using
	       "+<" works for symmetry,	but you	really should consider writing
	       something to the	temporary file first.  You will	need to	seek()
	       to do the reading.

	       Since v5.8.0, perl has built using PerlIO by default.  Unless
	       you've changed this (i.e. Configure -Uuseperlio), you can open
	       file handles to "in memory" files held in Perl scalars via:

		   open($fh, '>', \$variable) || ..

	       Though if you try to re-open "STDOUT" or	"STDERR" as an "in
	       memory" file, you have to close it first:

		   close STDOUT;
		   open	STDOUT,	'>', \$variable	or die "Can't open STDOUT: $!";

	       Examples:

		   $ARTICLE = 100;
		   open	ARTICLE	or die "Can't find article $ARTICLE: $!\n";
		   while (<ARTICLE>) {...

		   open(LOG, '>>/usr/spool/news/twitlog');     # (log is reserved)
		   # if	the open fails,	output is discarded

		   open(my $dbase, '+<', 'dbase.mine')	       # open for update
		       or die "Can't open 'dbase.mine' for update: $!";

		   open(my $dbase, '+<dbase.mine')		       # ditto
		       or die "Can't open 'dbase.mine' for update: $!";

		   open(ARTICLE, '-|', "caesar <$article")     # decrypt article
		       or die "Can't start caesar: $!";

		   open(ARTICLE, "caesar <$article |")	       # ditto
		       or die "Can't start caesar: $!";

		   open(EXTRACT, "|sort	>Tmp$$")	       # $$ is our process id
		       or die "Can't start sort: $!";

		   # in	memory files
		   open(MEMORY,'>', \$var)
		       or die "Can't open memory file: $!";
		   print MEMORY	"foo!\n";		       # output	will end up in $var

		   # process argument list of files along with any includes

		   foreach $file (@ARGV) {
		       process($file, 'fh00');
		   }

		   sub process {
		       my($filename, $input) = @_;
		       $input++;	       # this is a string increment
		       unless (open($input, $filename))	{
			   print STDERR	"Can't open $filename: $!\n";
			   return;
		       }

		       local $_;
		       while (<$input>)	{	       # note use of indirection
			   if (/^#include "(.*)"/) {
			       process($1, $input);
			       next;
			   }
			   #...		       # whatever
		       }
		   }

	       See perliol for detailed	info on	PerlIO.

	       You may also, in	the Bourne shell tradition, specify an EXPR
	       beginning with '>&', in which case the rest of the string is
	       interpreted as the name of a filehandle (or file	descriptor, if
	       numeric)	to be duped (as	dup(2))	and opened.  You may use "&"
	       after ">", ">>",	"<", "+>", "+>>", and "+<".  The mode you
	       specify should match the	mode of	the original filehandle.
	       (Duping a filehandle does not take into account any existing
	       contents	of IO buffers.)	If you use the 3-arg form then you can
	       pass either a number, the name of a filehandle or the normal
	       "reference to a glob".

	       Here is a script	that saves, redirects, and restores "STDOUT"
	       and "STDERR" using various methods:

		   #!/usr/bin/perl
		   open	my $oldout, ">&STDOUT"	   or die "Can't dup STDOUT: $!";
		   open	OLDERR,	    ">&", \*STDERR or die "Can't dup STDERR: $!";

		   open	STDOUT,	'>', "foo.out" or die "Can't redirect STDOUT: $!";
		   open	STDERR,	">&STDOUT"     or die "Can't dup STDOUT: $!";

		   select STDERR; $| = 1;      # make unbuffered
		   select STDOUT; $| = 1;      # make unbuffered

		   print STDOUT	"stdout	1\n";  # this works for
		   print STDERR	"stderr	1\n";  # subprocesses too

		   open	STDOUT,	">&", $oldout or die "Can't dup	\$oldout: $!";
		   open	STDERR,	">&OLDERR"    or die "Can't dup	OLDERR:	$!";

		   print STDOUT	"stdout	2\n";
		   print STDERR	"stderr	2\n";

	       If you specify '<&=X', where "X"	is a file descriptor number or
	       a filehandle, then Perl will do an equivalent of	C's "fdopen"
	       of that file descriptor (and not	call dup(2)); this is more
	       parsimonious of file descriptors.  For example:

		   # open for input, reusing the fileno	of $fd
		   open(FILEHANDLE, "<&=$fd")

	       or

		   open(FILEHANDLE, "<&=", $fd)

	       or

		   # open for append, using the	fileno of OLDFH
		   open(FH, ">>&=", OLDFH)

	       or

		   open(FH, ">>&=OLDFH")

	       Being parsimonious on filehandles is also useful	(besides being
	       parsimonious) for example when something	is dependent on	file
	       descriptors, like for example locking using flock().  If	you do
	       just "open(A, '>>&B')", the filehandle A	will not have the same
	       file descriptor as B, and therefore flock(A) will not flock(B),
	       and vice	versa.	But with "open(A, '>>&=B')" the	filehandles
	       will share the same file	descriptor.

	       Note that if you	are using Perls	older than 5.8.0, Perl will be
	       using the standard C libraries' fdopen()	to implement the "="
	       functionality.  On many UNIX systems fdopen() fails when	file
	       descriptors exceed a certain value, typically 255.  For Perls
	       5.8.0 and later,	PerlIO is most often the default.

	       You can see whether Perl	has been compiled with PerlIO or not
	       by running "perl	-V" and	looking	for "useperlio=" line.	If
	       "useperlio" is "define",	you have PerlIO, otherwise you don't.

	       If you open a pipe on the command '-', i.e., either '|-'	or
	       '-|' with 2-arguments (or 1-argument) form of open(), then
	       there is	an implicit fork done, and the return value of open is
	       the pid of the child within the parent process, and 0 within
	       the child process.  (Use	"defined($pid)"	to determine whether
	       the open	was successful.)  The filehandle behaves normally for
	       the parent, but i/o to that filehandle is piped from/to the
	       STDOUT/STDIN of the child process.  In the child	process	the
	       filehandle isn't	opened--i/o happens from/to the	new STDOUT or
	       STDIN.  Typically this is used like the normal piped open when
	       you want	to exercise more control over just how the pipe	com-
	       mand gets executed, such	as when	you are	running	setuid,	and
	       don't want to have to scan shell	commands for metacharacters.
	       The following triples are more or less equivalent:

		   open(FOO, "|tr '[a-z]' '[A-Z]'");
		   open(FOO, '|-', "tr '[a-z]' '[A-Z]'");
		   open(FOO, '|-') || exec 'tr', '[a-z]', '[A-Z]';
		   open(FOO, '|-', "tr", '[a-z]', '[A-Z]');

		   open(FOO, "cat -n '$file'|");
		   open(FOO, '-|', "cat	-n '$file'");
		   open(FOO, '-|') || exec 'cat', '-n',	$file;
		   open(FOO, '-|', "cat", '-n',	$file);

	       The last	example	in each	block shows the	pipe as	"list form",
	       which is	not yet	supported on all platforms.  A good rule of
	       thumb is	that if	your platform has true "fork()"	(in other
	       words, if your platform is UNIX)	you can	use the	list form.

	       See "Safe Pipe Opens" in	perlipc	for more examples of this.

	       Beginning with v5.6.0, Perl will	attempt	to flush all files
	       opened for output before	any operation that may do a fork, but
	       this may	not be supported on some platforms (see	perlport).  To
	       be safe,	you may	need to	set $| ($AUTOFLUSH in English) or call
	       the "autoflush()" method	of "IO::Handle"	on any open handles.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened	file descriptor	as determined
	       by the value of $^F.  See "$^F" in perlvar.

	       Closing any piped filehandle causes the parent process to wait
	       for the child to	finish,	and returns the	status value in	$? and
	       "${^CHILD_ERROR_NATIVE}".

	       The filename passed to 2-argument (or 1-argument) form of
	       open() will have	leading	and trailing whitespace	deleted, and
	       the normal redirection characters honored.  This	property,
	       known as	"magic open", can often	be used	to good	effect.	 A
	       user could specify a filename of	"rsh cat file |", or you could
	       change certain filenames	as needed:

		   $filename =~	s/(.*\.gz)\s*$/gzip -dc	< $1|/;
		   open(FH, $filename) or die "Can't open $filename: $!";

	       Use 3-argument form to open a file with arbitrary weird charac-
	       ters in it,

		   open(FOO, '<', $file);

	       otherwise it's necessary	to protect any leading and trailing
	       whitespace:

		   $file =~ s#^(\s)#./$1#;
		   open(FOO, "<	$file\0");

	       (this may not work on some bizarre filesystems).	 One should
	       conscientiously choose between the magic	and 3-arguments	form
	       of open():

		   open	IN, $ARGV[0];

	       will allow the user to specify an argument of the form "rsh cat
	       file |",	but will not work on a filename	which happens to have
	       a trailing space, while

		   open	IN, '<', $ARGV[0];

	       will have exactly the opposite restrictions.

	       If you want a "real" C "open" (see open(2) on your system),
	       then you	should use the "sysopen" function, which involves no
	       such magic (but may use subtly different	filemodes than Perl
	       open(), which is	mapped to C fopen()).  This is another way to
	       protect your filenames from interpretation.  For	example:

		   use IO::Handle;
		   sysopen(HANDLE, $path, O_RDWR|O_CREAT|O_EXCL)
		       or die "sysopen $path: $!";
		   $oldfh = select(HANDLE); $| = 1; select($oldfh);
		   print HANDLE	"stuff $$\n";
		   seek(HANDLE,	0, 0);
		   print "File contains: ", <HANDLE>;

	       Using the constructor from the "IO::Handle" package (or one of
	       its subclasses, such as "IO::File" or "IO::Socket"), you	can
	       generate	anonymous filehandles that have	the scope of whatever
	       variables hold references to them, and automatically close
	       whenever	and however you	leave that scope:

		   use IO::File;
		   #...
		   sub read_myfile_munged {
		       my $ALL = shift;
		       my $handle = IO::File->new;
		       open($handle, "myfile") or die "myfile: $!";
		       $first =	<$handle>
			   or return ();     # Automatically closed here.
		       mung $first or die "mung	failed";       # Or here.
		       return $first, <$handle>	if $ALL;       # Or here.
		       $first;				       # Or here.
		   }

	       See "seek" for some details about mixing	reading	and writing.

       opendir DIRHANDLE,EXPR
	       Opens a directory named EXPR for	processing by "readdir",
	       "telldir", "seekdir", "rewinddir", and "closedir".  Returns
	       true if successful.  DIRHANDLE may be an	expression whose value
	       can be used as an indirect dirhandle, usually the real dirhan-
	       dle name.  If DIRHANDLE is an undefined scalar variable (or ar-
	       ray or hash element), the variable is assigned a	reference to a
	       new anonymous dirhandle.	 DIRHANDLEs have their own namespace
	       separate	from FILEHANDLEs.

	       See example at "readdir".

       ord EXPR
       ord     Returns the numeric (the	native 8-bit encoding, like ASCII or
	       EBCDIC, or Unicode) value of the	first character	of EXPR.  If
	       EXPR is omitted,	uses $_.

	       For the reverse,	see "chr".  See	perlunicode for	more about
	       Unicode.

       our EXPR
       our EXPR	TYPE
       our EXPR	: ATTRS
       our TYPE	EXPR : ATTRS
	       "our" associates	a simple name with a package variable in the
	       current package for use within the current scope.  When "use
	       strict 'vars'" is in effect, "our" lets you use declared	global
	       variables without qualifying them with package names, within
	       the lexical scope of the	"our" declaration.  In this way	"our"
	       differs from "use vars",	which is package scoped.

	       Unlike "my", which both allocates storage for a variable	and
	       associates a simple name	with that storage for use within the
	       current scope, "our" associates a simple	name with a package
	       variable	in the current package,	for use	within the current
	       scope.  In other	words, "our" has the same scoping rules	as
	       "my", but does not necessarily create a variable.

	       If more than one	value is listed, the list must be placed in
	       parentheses.

		   our $foo;
		   our($bar, $baz);

	       An "our"	declaration declares a global variable that will be
	       visible across its entire lexical scope,	even across package
	       boundaries.  The	package	in which the variable is entered is
	       determined at the point of the declaration, not at the point of
	       use.  This means	the following behavior holds:

		   package Foo;
		   our $bar;	       # declares $Foo::bar for	rest of	lexical	scope
		   $bar	= 20;

		   package Bar;
		   print $bar;	       # prints	20, as it refers to $Foo::bar

	       Multiple	"our" declarations with	the same name in the same lex-
	       ical scope are allowed if they are in different packages.  If
	       they happen to be in the	same package, Perl will	emit warnings
	       if you have asked for them, just	like multiple "my" declara-
	       tions.  Unlike a	second "my" declaration, which will bind the
	       name to a fresh variable, a second "our"	declaration in the
	       same package, in	the same scope,	is merely redundant.

		   use warnings;
		   package Foo;
		   our $bar;	       # declares $Foo::bar for	rest of	lexical	scope
		   $bar	= 20;

		   package Bar;
		   our $bar = 30;      # declares $Bar::bar for	rest of	lexical	scope
		   print $bar;	       # prints	30

		   our $bar;	       # emits warning but has no other	effect
		   print $bar;	       # still prints 30

	       An "our"	declaration may	also have a list of attributes associ-
	       ated with it.

	       The exact semantics and interface of TYPE and ATTRS are still
	       evolving.  TYPE is currently bound to the use of	"fields"
	       pragma, and attributes are handled using	the "attributes"
	       pragma, or starting from	Perl 5.8.0 also	via the	"Attri-
	       bute::Handlers" module.	See "Private Variables via my()" in
	       perlsub for details, and	fields,	attributes, and	Attri-
	       bute::Handlers.

	       The only	currently recognized "our()" attribute is "unique"
	       which indicates that a single copy of the global	is to be used
	       by all interpreters should the program happen to	be running in
	       a multi-interpreter environment.	(The default behaviour would
	       be for each interpreter to have its own copy of the global.)
	       Examples:

		   our @EXPORT : unique	= qw(foo);
		   our %EXPORT_TAGS : unique = (bar => [qw(aa bb cc)]);
		   our $VERSION	: unique = "1.00";

	       Note that this attribute	also has the effect of making the
	       global readonly when the	first new interpreter is cloned	(for
	       example,	when the first new thread is created).

	       Multi-interpreter environments can come to being	either through
	       the fork() emulation on Windows platforms, or by	embedding perl
	       in a multi-threaded application.	 The "unique" attribute	does
	       nothing in all other environments.

	       Warning:	the current implementation of this attribute operates
	       on the typeglob associated with the variable; this means	that
	       "our $x : unique" also has the effect of	"our @x	: unique; our
	       %x : unique". This may be subject to change.

       pack TEMPLATE,LIST
	       Takes a LIST of values and converts it into a string using the
	       rules given by the TEMPLATE.  The resulting string is the con-
	       catenation of the converted values.  Typically, each converted
	       value looks like	its machine-level representation.  For exam-
	       ple, on 32-bit machines an integer may be represented by	a se-
	       quence of 4 bytes which will be converted to a sequence of 4
	       characters.

	       The TEMPLATE is a sequence of characters	that give the order
	       and type	of values, as follows:

		   a   A string	with arbitrary binary data, will be null padded.
		   A   A text (ASCII) string, will be space padded.
		   Z   A null terminated (ASCIZ) string, will be null padded.

		   b   A bit string (ascending bit order inside	each byte, like	vec()).
		   B   A bit string (descending	bit order inside each byte).
		   h   A hex string (low nybble	first).
		   H   A hex string (high nybble first).

		   c   A signed	char value.
		   C   An unsigned C char (octet) even under Unicode.

		   s   A signed	short value.
		   S   An unsigned short value.
			 (This 'short' is _exactly_ 16 bits, which may differ from
			  what a local C compiler calls	'short'.  If you want
			  native-length	shorts,	use the	'!' suffix.)

		   i   A signed	integer	value.
		   I   An unsigned integer value.
			 (This 'integer' is _at_least_ 32 bits wide.  Its exact
			  size depends on what a local C compiler calls	'int',
			  and may even be larger than the 'long' described in
			  the next item.)

		   l   A signed	long value.
		   L   An unsigned long	value.
			 (This 'long' is _exactly_ 32 bits, which may differ from
			  what a local C compiler calls	'long'.	 If you	want
			  native-length	longs, use the '!' suffix.)

		   n   An unsigned short in "network" (big-endian) order.
		   N   An unsigned long	in "network" (big-endian) order.
		   v   An unsigned short in "VAX" (little-endian) order.
		   V   An unsigned long	in "VAX" (little-endian) order.
			 (These	'shorts' and 'longs' are _exactly_ 16 bits and
			  _exactly_ 32 bits, respectively.)

		   q   A signed	quad (64-bit) value.
		   Q   An unsigned quad	value.
			 (Quads	are available only if your system supports 64-bit
			  integer values _and_ if Perl has been	compiled to support those.
			  Causes a fatal error otherwise.)

		   j   A signed	integer	value (a Perl internal integer,	IV).
		   J   An unsigned integer value (a Perl internal unsigned integer, UV).

		   f   A single-precision float	in the native format.
		   d   A double-precision float	in the native format.

		   F   A floating point	value in the native native format
			  (a Perl internal floating point value, NV).
		   D   A long double-precision float in	the native format.
			 (Long doubles are available only if your system supports long
			  double values	_and_ if Perl has been compiled	to support those.
			  Causes a fatal error otherwise.)

		   p   A pointer to a null-terminated string.
		   P   A pointer to a structure	(fixed-length string).

		   u   A uuencoded string.
		   U   A Unicode character number.  Encodes to UTF-8 internally
		       (or UTF-EBCDIC in EBCDIC	platforms).

		   w   A BER compressed	integer	(not an	ASN.1 BER, see perlpacktut for
		       details).  Its bytes represent an unsigned integer in base 128,
		       most significant	digit first, with as few digits	as possible.  Bit
		       eight (the high bit) is set on each byte	except the last.

		   x   A null byte.
		   X   Back up a byte.
		   @   Null fill to absolute position, counted from the	start of
		       the innermost ()-group.
		   (   Start of	a ()-group.

	       The following rules apply:

	       *       Each letter may optionally be followed by a number giv-
		       ing a repeat count.  With all types except "a", "A",
		       "Z", "b", "B", "h", "H",	"@", "x", "X" and "P" the pack
		       function	will gobble up that many values	from the LIST.
		       A "*" for the repeat count means	to use however many
		       items are left, except for "@", "x", "X", where it is
		       equivalent to 0,	and "u", where it is equivalent	to 1
		       (or 45, what is the same).  A numeric repeat count may
		       optionally be enclosed in brackets, as in "pack
		       'C[80]',	@arr".

		       One can replace the numeric repeat count	by a template
		       enclosed	in brackets; then the packed length of this
		       template	in bytes is used as a count.  For example,
		       "x[L]" skips a long (it skips the number	of bytes in a
		       long); the template "$t X[$t] $t" unpack()s twice what
		       $t unpacks.  If the template in brackets	contains
		       alignment commands (such	as "x![d]"), its packed	length
		       is calculated as	if the start of	the template has the
		       maximal possible	alignment.

		       When used with "Z", "*" results in the addition of a
		       trailing	null byte (so the packed result	will be	one
		       longer than the byte "length" of	the item).

		       When used with "@", the repeat count represents an off-
		       set from	the start of the innermost () group.

		       The repeat count	for "u"	is interpreted as the maximal
		       number of bytes to encode per line of output, with 0, 1
		       and 2 replaced by 45. The repeat	count should not be
		       more than 65.

	       *       The "a",	"A", and "Z" types gobble just one value, but
		       pack it as a string of length count, padding with nulls
		       or spaces as necessary.	When unpacking,	"A" strips
		       trailing	whitespace and nulls, "Z" strips everything
		       after the first null, and "a" returns data verbatim.

		       If the value-to-pack is too long, it is truncated.  If
		       too long	and an explicit	count is provided, "Z" packs
		       only "$count-1" bytes, followed by a null byte.	Thus
		       "Z" always packs	a trailing null	(except	when the count
		       is 0).

	       *       Likewise, the "b" and "B" fields	pack a string that
		       many bits long.	Each character of the input field of
		       pack() generates	1 bit of the result.  Each result bit
		       is based	on the least-significant bit of	the corre-
		       sponding	input character, i.e., on "ord($char)%2".  In
		       particular, characters "0" and "1" generate bits	0 and
		       1, as do	characters "\0"	and "\1".

		       Starting	from the beginning of the input	string of
		       pack(), each 8-tuple of characters is converted to 1
		       character of output.  With format "b" the first charac-
		       ter of the 8-tuple determines the least-significant bit
		       of a character, and with	format "B" it determines the
		       most-significant	bit of a character.

		       If the length of	the input string is not	exactly	divis-
		       ible by 8, the remainder	is packed as if	the input
		       string were padded by null characters at	the end.  Sim-
		       ilarly, during unpack()ing the "extra" bits are ig-
		       nored.

		       If the input string of pack() is	longer than needed,
		       extra characters	are ignored. A "*" for the repeat
		       count of	pack() means to	use all	the characters of the
		       input field.  On	unpack()ing the	bits are converted to
		       a string	of "0"s	and "1"s.

	       *       The "h" and "H" fields pack a string that many nybbles
		       (4-bit groups, representable as hexadecimal digits,
		       0-9a-f) long.

		       Each character of the input field of pack() generates 4
		       bits of the result.  For	non-alphabetical characters
		       the result is based on the 4 least-significant bits of
		       the input character, i.e., on "ord($char)%16".  In par-
		       ticular,	characters "0" and "1" generate	nybbles	0 and
		       1, as do	bytes "\0" and "\1".  For characters "a".."f"
		       and "A".."F" the	result is compatible with the usual
		       hexadecimal digits, so that "a" and "A" both generate
		       the nybble "0xa==10".  The result for characters
		       "g".."z"	and "G".."Z" is	not well-defined.

		       Starting	from the beginning of the input	string of
		       pack(), each pair of characters is converted to 1 char-
		       acter of	output.	 With format "h" the first character
		       of the pair determines the least-significant nybble of
		       the output character, and with format "H" it determines
		       the most-significant nybble.

		       If the length of	the input string is not	even, it be-
		       haves as	if padded by a null character at the end.
		       Similarly, during unpack()ing the "extra" nybbles are
		       ignored.

		       If the input string of pack() is	longer than needed,
		       extra characters	are ignored.  A	"*" for	the repeat
		       count of	pack() means to	use all	the characters of the
		       input field.  On	unpack()ing the	nybbles	are converted
		       to a string of hexadecimal digits.

	       *       The "p" type packs a pointer to a null-terminated
		       string.	You are	responsible for	ensuring the string is
		       not a temporary value (which can	potentially get	de-
		       allocated before	you get	around to using	the packed re-
		       sult).  The "P" type packs a pointer to a structure of
		       the size	indicated by the length.  A NULL pointer is
		       created if the corresponding value for "p" or "P" is
		       "undef",	similarly for unpack().

	       *       The "/" template	character allows packing and unpacking
		       of a sequence of	items where the	packed structure con-
		       tains a packed item count followed by the packed	items
		       themselves.

		       For "pack" you write length-item"/"sequence-item	and
		       the length-item describes how the length	value is
		       packed. The ones	likely to be of	most use are integer-
		       packing ones like "n" (for Java strings), "w" (for
		       ASN.1 or	SNMP) and "N" (for Sun XDR).

		       For "pack", the sequence-item may have a	repeat count,
		       in which	case the minimum of that and the number	of
		       available items is used as argument for the length-
		       item. If	it has no repeat count or uses a '*', the num-
		       ber of available	items is used.

		       For "unpack" an internal	stack of integer arguments un-
		       packed so far is	used. You write	"/"sequence-item and
		       the repeat count	is obtained by popping off the last
		       element from the	stack. The sequence-item must not have
		       a repeat	count.

		       If the sequence-item refers to a	string type ("A", "a"
		       or "Z"),	the length-item	is a string length, not	a num-
		       ber of strings. If there	is an explicit repeat count
		       for pack, the packed string will	be adjusted to that
		       given length.

			   unpack 'C/a', "\04Gurusamy";		   gives ('Guru')
			   unpack 'a3/A	A*', '007 Bond	J ';	   gives (' Bond', 'J')
			   unpack 'a3 x2 /A A*', '007: Bond, J.';  gives ('Bond, J', '.')
			   pack	'n/a* w/a*','hello,','world';	   gives "\000\006hello,\005world"
			   pack	'a/C2',	ord('a') .. ord('z');	   gives '2ab'

		       The length-item is not returned explicitly from "un-
		       pack".

		       Adding a	count to the length-item letter	is unlikely to
		       do anything useful, unless that letter is "A", "a" or
		       "Z".  Packing with a length-item	of "a" or "Z" may in-
		       troduce "\000" characters, which	Perl does not regard
		       as legal	in numeric strings.

	       *       The integer types "s", "S", "l",	and "L"	may be immedi-
		       ately followed by a "!" suffix to signify native	shorts
		       or longs--as you	can see	from above for example a bare
		       "l" does	mean exactly 32	bits, the native "long"	(as
		       seen by the local C compiler) may be larger.  This is
		       an issue	mainly in 64-bit platforms.  You can see
		       whether using "!" makes any difference by

			       print length(pack("s")),	" ", length(pack("s!")), "\n";
			       print length(pack("l")),	" ", length(pack("l!")), "\n";

		       "i!" and	"I!" also work but only	because	of complete-
		       ness; they are identical	to "i" and "I".

		       The actual sizes	(in bytes) of native shorts, ints,
		       longs, and long longs on	the platform where Perl	was
		       built are also available	via Config:

			      use Config;
			      print $Config{shortsize},	   "\n";
			      print $Config{intsize},	   "\n";
			      print $Config{longsize},	   "\n";
			      print $Config{longlongsize}, "\n";

		       (The $Config{longlongsize} will be undefined if your
		       system does not support long longs.)

	       *       The integer formats "s",	"S", "i", "I", "l", "L", "j",
		       and "J" are inherently non-portable between processors
		       and operating systems because they obey the native by-
		       teorder and endianness.	For example a 4-byte integer
		       0x12345678 (305419896 decimal) would be ordered na-
		       tively (arranged	in and handled by the CPU registers)
		       into bytes as

			       0x12 0x34 0x56 0x78     # big-endian
			       0x78 0x56 0x34 0x12     # little-endian

		       Basically, the Intel and	VAX CPUs are little-endian,
		       while everybody else, for example Motorola m68k/88k,
		       PPC, Sparc, HP PA, Power, and Cray are big-endian.  Al-
		       pha and MIPS can	be either: Digital/Compaq used/uses
		       them in little-endian mode; SGI/Cray uses them in big-
		       endian mode.

		       The names `big-endian' and `little-endian' are comic
		       references to the classic "Gulliver's Travels" (via the
		       paper "On Holy Wars and a Plea for Peace" by Danny
		       Cohen, USC/ISI IEN 137, April 1,	1980) and the egg-eat-
		       ing habits of the Lilliputians.

		       Some systems may	have even weirder byte orders such as

			       0x56 0x78 0x12 0x34
			       0x34 0x12 0x78 0x56

		       You can see your	system's preference with

			       print join(" ", map { sprintf "%#02x", $_ }
						   unpack("C*",pack("L",0x12345678))), "\n";

		       The byteorder on	the platform where Perl	was built is
		       also available via Config:

			       use Config;
			       print $Config{byteorder}, "\n";

		       Byteorders '1234' and '12345678'	are little-endian,
		       '4321' and '87654321' are big-endian.

		       If you want portable packed integers use	the formats
		       "n", "N", "v", and "V", their byte endianness and size
		       are known.  See also perlport.

	       *       Real numbers (floats and	doubles) are in	the native ma-
		       chine format only; due to the multiplicity of floating
		       formats around, and the lack of a standard "network"
		       representation, no facility for interchange has been
		       made.  This means that packed floating point data writ-
		       ten on one machine may not be readable on another -
		       even if both use	IEEE floating point arithmetic (as the
		       endian-ness of the memory representation	is not part of
		       the IEEE	spec).	See also perlport.

		       Note that Perl uses doubles internally for all numeric
		       calculation, and	converting from	double into float and
		       thence back to double again will	lose precision (i.e.,
		       "unpack("f", pack("f", $foo)") will not in general
		       equal $foo).

	       *       If the pattern begins with a "U", the resulting string
		       will be treated as UTF-8-encoded	Unicode. You can force
		       UTF-8 encoding on in a string with an initial "U0", and
		       the bytes that follow will be interpreted as Unicode
		       characters. If you don't	want this to happen, you can
		       begin your pattern with "C0" (or	anything else) to
		       force Perl not to UTF-8 encode your string, and then
		       follow this with	a "U*" somewhere in your pattern.

	       *       You must	yourself do any	alignment or padding by	in-
		       serting for example enough 'x'es	while packing.	There
		       is no way to pack() and unpack()	could know where the
		       characters are going to or coming from.	Therefore
		       "pack" (and "unpack") handle their output and input as
		       flat sequences of characters.

	       *       A ()-group is a sub-TEMPLATE enclosed in	parentheses.
		       A group may take	a repeat count,	both as	postfix, and
		       for unpack() also via the "/" template character.
		       Within each repetition of a group, positioning with "@"
		       starts again at 0. Therefore, the result	of

			   pack( '@1A((@2A)@3A)', 'a', 'b', 'c'	)

		       is the string "\0a\0\0bc".

	       *       "x" and "X" accept "!" modifier.	 In this case they act
		       as alignment commands: they jump	forward/back to	the
		       closest position	aligned	at a multiple of "count" char-
		       acters. For example, to pack() or unpack() C's "struct
		       {char c;	double d; char cc[2]}" one may need to use the
		       template	"W x![d] d W[2]"; this assumes that doubles
		       must be aligned on the double's size.

		       For alignment commands "count" of 0 is equivalent to
		       "count" of 1; both result in no-ops.

	       *       A comment in a TEMPLATE starts with "#" and goes	to the
		       end of line.  White space may be	used to	separate pack
		       codes from each other, but a "!"	modifier and a repeat
		       count must follow immediately.

	       *       If TEMPLATE requires more arguments to pack() than ac-
		       tually given, pack() assumes additional "" arguments.
		       If TEMPLATE requires fewer arguments to pack() than ac-
		       tually given, extra arguments are ignored.

	       Examples:

		   $foo	= pack("CCCC",65,66,67,68);
		   # foo eq "ABCD"
		   $foo	= pack("C4",65,66,67,68);
		   # same thing
		   $foo	= pack("W4",0x24b6,0x24b7,0x24b8,0x24b9);
		   # same thing	with Unicode circled letters.
		   $foo	= pack("U4",0x24b6,0x24b7,0x24b8,0x24b9);
		   # same thing	with Unicode circled letters.

		   $foo	= pack("ccxxcc",65,66,67,68);
		   # foo eq "AB\0\0CD"

		   # note: the above examples featuring	"C" and	"c" are	true
		   # only on ASCII and ASCII-derived systems such as ISO Latin 1
		   # and UTF-8.	 In EBCDIC the first example would be
		   # $foo = pack("CCCC",193,194,195,196);

		   $foo	= pack("s2",1,2);
		   # "\1\0\2\0"	on little-endian
		   # "\0\1\0\2"	on big-endian

		   $foo	= pack("a4","abcd","x","y","z");
		   # "abcd"

		   $foo	= pack("aaaa","abcd","x","y","z");
		   # "axyz"

		   $foo	= pack("a14","abcdefg");
		   # "abcdefg\0\0\0\0\0\0\0"

		   $foo	= pack("i9pl", gmtime);
		   # a real struct tm (on my system anyway)

		   $utmp_template = "Z8	Z8 Z16 L";
		   $utmp = pack($utmp_template,	@utmp1);
		   # a struct utmp (BSDish)

		   @utmp2 = unpack($utmp_template, $utmp);
		   # "@utmp1" eq "@utmp2"

		   sub bintodec	{
		       unpack("N", pack("B32", substr("0" x 32 . shift,	-32)));
		   }

		   $foo	= pack('sx2l', 12, 34);
		   # short 12, two zero	bytes padding, long 34
		   $bar	= pack('s@4l', 12, 34);
		   # short 12, zero fill to position 4,	long 34
		   # $foo eq $bar

	       The same	template may generally also be used in unpack().

       package NAMESPACE
       package Declares	the compilation	unit as	being in the given namespace.
	       The scope of the	package	declaration is from the	declaration
	       itself through the end of the enclosing block, file, or eval
	       (the same as the	"my" operator).	 All further unqualified dy-
	       namic identifiers will be in this namespace.  A package state-
	       ment affects only dynamic variables--including those you've
	       used "local" on--but not	lexical	variables, which are created
	       with "my".  Typically it	would be the first declaration in a
	       file to be included by the "require" or "use" operator.	You
	       can switch into a package in more than one place; it merely in-
	       fluences	which symbol table is used by the compiler for the
	       rest of that block.  You	can refer to variables and filehandles
	       in other	packages by prefixing the identifier with the package
	       name and	a double colon:	 $Package::Variable.  If the package
	       name is null, the "main"	package	as assumed.  That is, $::sail
	       is equivalent to	$main::sail (as	well as	to $main'sail, still
	       seen in older code).

	       If NAMESPACE is omitted,	then there is no current package, and
	       all identifiers must be fully qualified or lexicals.  However,
	       you are strongly	advised	not to make use	of this	feature. Its
	       use can cause unexpected	behaviour, even	crashing some versions
	       of Perl.	It is deprecated, and will be removed from a future
	       release.

	       See "Packages" in perlmod for more information about packages,
	       modules,	and classes.  See perlsub for other scoping issues.

       pipe READHANDLE,WRITEHANDLE
	       Opens a pair of connected pipes like the	corresponding system
	       call.  Note that	if you set up a	loop of	piped processes, dead-
	       lock can	occur unless you are very careful.  In addition, note
	       that Perl's pipes use IO	buffering, so you may need to set $|
	       to flush	your WRITEHANDLE after each command, depending on the
	       application.

	       See IPC::Open2, IPC::Open3, and "Bidirectional Communication"
	       in perlipc for examples of such things.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened	file descriptors as determined
	       by the value of $^F.  See "$^F" in perlvar.

       pop ARRAY
       pop     Pops and	returns	the last value of the array, shortening	the
	       array by	one element.

	       If there	are no elements	in the array, returns the undefined
	       value (although this may	happen at other	times as well).	 If
	       ARRAY is	omitted, pops the @ARGV	array in the main program, and
	       the @_ array in subroutines, just like "shift".

       pos SCALAR
       pos     Returns the offset of where the last "m//g" search left off for
	       the variable in question	($_ is used when the variable is not
	       specified).  Note that 0	is a valid match offset.  "undef" in-
	       dicates that the	search position	is reset (usually due to match
	       failure,	but can	also be	because	no match has yet been per-
	       formed on the scalar). "pos" directly accesses the location
	       used by the regexp engine to store the offset, so assigning to
	       "pos" will change that offset, and so will also influence the
	       "\G" zero-width assertion in regular expressions. Because a
	       failed "m//gc" match doesn't reset the offset, the return from
	       "pos" won't change either in this case.	See perlre and perlop.

       print FILEHANDLE	LIST
       print LIST
       print   Prints a	string or a list of strings.  Returns true if success-
	       ful.  FILEHANDLE	may be a scalar	variable name, in which	case
	       the variable contains the name of or a reference	to the file-
	       handle, thus introducing	one level of indirection.  (NOTE: If
	       FILEHANDLE is a variable	and the	next token is a	term, it may
	       be misinterpreted as an operator	unless you interpose a "+" or
	       put parentheses around the arguments.)  If FILEHANDLE is	omit-
	       ted, prints by default to standard output (or to	the last se-
	       lected output channel--see "select").  If LIST is also omitted,
	       prints $_ to the	currently selected output channel.  To set the
	       default output channel to something other than STDOUT use the
	       select operation.  The current value of $, (if any) is printed
	       between each LIST item.	The current value of "$\" (if any) is
	       printed after the entire	LIST has been printed.	Because	print
	       takes a LIST, anything in the LIST is evaluated in list con-
	       text, and any subroutine	that you call will have	one or more of
	       its expressions evaluated in list context.  Also	be careful not
	       to follow the print keyword with	a left parenthesis unless you
	       want the	corresponding right parenthesis	to terminate the argu-
	       ments to	the print--interpose a "+" or put parentheses around
	       all the arguments.

	       Note that if you're storing FILEHANDLEs in an array, or if
	       you're using any	other expression more complex than a scalar
	       variable	to retrieve it,	you will have to use a block returning
	       the filehandle value instead:

		   print { $files[$i] }	"stuff\n";
		   print { $OK ? STDOUT	: STDERR } "stuff\n";

       printf FILEHANDLE FORMAT, LIST
       printf FORMAT, LIST
	       Equivalent to "print FILEHANDLE sprintf(FORMAT, LIST)", except
	       that "$\" (the output record separator) is not appended.	 The
	       first argument of the list will be interpreted as the "printf"
	       format. See "sprintf" for an explanation	of the format argu-
	       ment.  If "use locale" is in effect, and	POSIX::setlocale() has
	       been called, the	character used for the decimal separator in
	       formatted floating point	numbers	is affected by the LC_NUMERIC
	       locale.	See perllocale and POSIX.

	       Don't fall into the trap	of using a "printf" when a simple
	       "print" would do.  The "print" is more efficient	and less error
	       prone.

       prototype FUNCTION
	       Returns the prototype of	a function as a	string (or "undef" if
	       the function has	no prototype).	FUNCTION is a reference	to, or
	       the name	of, the	function whose prototype you want to retrieve.

	       If FUNCTION is a	string starting	with "CORE::", the rest	is
	       taken as	a name for Perl	builtin.  If the builtin is not	over-
	       ridable (such as	"qw//")	or if its arguments cannot be ade-
	       quately expressed by a prototype	(such as "system"), proto-
	       type() returns "undef", because the builtin does	not really be-
	       have like a Perl	function.  Otherwise, the string describing
	       the equivalent prototype	is returned.

       push ARRAY,LIST
	       Treats ARRAY as a stack,	and pushes the values of LIST onto the
	       end of ARRAY.  The length of ARRAY increases by the length of
	       LIST.  Has the same effect as

		   for $value (LIST) {
		       $ARRAY[++$#ARRAY] = $value;
		   }

	       but is more efficient.  Returns the number of elements in the
	       array following the completed "push".

       q/STRING/
       qq/STRING/
       qx/STRING/
       qw/STRING/
	       Generalized quotes.  See	"Quote-Like Operators" in perlop.

       qr/STRING/
	       Regexp-like quote.  See "Regexp Quote-Like Operators" in	per-
	       lop.

       quotemeta EXPR
       quotemeta
	       Returns the value of EXPR with all non-"word" characters	back-
	       slashed.	 (That is, all characters not matching
	       "/[A-Za-z_0-9]/"	will be	preceded by a backslash	in the re-
	       turned string, regardless of any	locale settings.)  This	is the
	       internal	function implementing the "\Q" escape in double-quoted
	       strings.

	       If EXPR is omitted, uses	$_.

       rand EXPR
       rand    Returns a random	fractional number greater than or equal	to 0
	       and less	than the value of EXPR.	 (EXPR should be positive.)
	       If EXPR is omitted, the value 1 is used.	 Currently EXPR	with
	       the value 0 is also special-cased as 1 -	this has not been doc-
	       umented before perl 5.8.0 and is	subject	to change in future
	       versions	of perl.  Automatically	calls "srand" unless "srand"
	       has already been	called.	 See also "srand".

	       Apply "int()" to	the value returned by "rand()" if you want
	       random integers instead of random fractional numbers.  For ex-
	       ample,

		   int(rand(10))

	       returns a random	integer	between	0 and 9, inclusive.

	       (Note: If your rand function consistently returns numbers that
	       are too large or	too small, then	your version of	Perl was prob-
	       ably compiled with the wrong number of RANDBITS.)

       read FILEHANDLE,SCALAR,LENGTH,OFFSET
       read FILEHANDLE,SCALAR,LENGTH
	       Attempts	to read	LENGTH characters of data into variable	SCALAR
	       from the	specified FILEHANDLE.  Returns the number of charac-
	       ters actually read, 0 at	end of file, or	undef if there was an
	       error (in the latter case $! is also set).  SCALAR will be
	       grown or	shrunk so that the last	character actually read	is the
	       last character of the scalar after the read.

	       An OFFSET may be	specified to place the read data at some place
	       in the string other than	the beginning.	A negative OFFSET
	       specifies placement at that many	characters counting backwards
	       from the	end of the string.  A positive OFFSET greater than the
	       length of SCALAR	results	in the string being padded to the re-
	       quired size with	"\0" bytes before the result of	the read is
	       appended.

	       The call	is actually implemented	in terms of either Perl's or
	       system's	fread()	call.  To get a	true read(2) system call, see
	       "sysread".

	       Note the	characters: depending on the status of the filehandle,
	       either (8-bit) bytes or characters are read.  By	default	all
	       filehandles operate on bytes, but for example if	the filehandle
	       has been	opened with the	":utf8"	I/O layer (see "open", and the
	       "open" pragma, open), the I/O will operate on UTF-8 encoded
	       Unicode characters, not bytes.  Similarly for the ":encoding"
	       pragma: in that case pretty much	any characters can be read.

       readdir DIRHANDLE
	       Returns the next	directory entry	for a directory	opened by
	       "opendir".  If used in list context, returns all	the rest of
	       the entries in the directory.  If there are no more entries,
	       returns an undefined value in scalar context or a null list in
	       list context.

	       If you're planning to filetest the return values	out of a
	       "readdir", you'd	better prepend the directory in	question.
	       Otherwise, because we didn't "chdir" there, it would have been
	       testing the wrong file.

		   opendir(my $dh, $some_dir) || die "can't opendir $some_dir: $!";
		   @dots = grep	{ /^\./	&& -f "$some_dir/$_" } readdir($dh);
		   closedir $dh;

       readline	EXPR
	       Reads from the filehandle whose typeglob	is contained in	EXPR.
	       In scalar context, each call reads and returns the next line,
	       until end-of-file is reached, whereupon the subsequent call re-
	       turns undef.  In	list context, reads until end-of-file is
	       reached and returns a list of lines.  Note that the notion of
	       "line" used here	is however you may have	defined	it with	$/ or
	       $INPUT_RECORD_SEPARATOR).  See "$/" in perlvar.

	       When $/ is set to "undef", when readline() is in	scalar context
	       (i.e. file slurp	mode), and when	an empty file is read, it re-
	       turns ''	the first time,	followed by "undef" subsequently.

	       This is the internal function implementing the "<EXPR>" opera-
	       tor, but	you can	use it directly.  The "<EXPR>" operator	is
	       discussed in more detail	in "I/O	Operators" in perlop.

		   $line = <STDIN>;
		   $line = readline(*STDIN);	       # same thing

	       If readline encounters an operating system error, $! will be
	       set with	the corresponding error	message.  It can be helpful to
	       check $!	when you are reading from filehandles you don't	trust,
	       such as a tty or	a socket.  The following example uses the op-
	       erator form of "readline", and takes the	necessary steps	to en-
	       sure that "readline" was	successful.

		   for (;;) {
		       undef $!;
		       unless (defined(	$line =	<> )) {
			   die $! if $!;
			   last; # reached EOF
		       }
		       # ...
		   }

       readlink	EXPR
       readlink
	       Returns the value of a symbolic link, if	symbolic links are im-
	       plemented.  If not, gives a fatal error.	 If there is some sys-
	       tem error, returns the undefined	value and sets $! (errno).  If
	       EXPR is omitted,	uses $_.

       readpipe	EXPR
	       EXPR is executed	as a system command.  The collected standard
	       output of the command is	returned.  In scalar context, it comes
	       back as a single	(potentially multi-line) string.  In list con-
	       text, returns a list of lines (however you've defined lines
	       with $/ or $INPUT_RECORD_SEPARATOR).  This is the internal
	       function	implementing the "qx/EXPR/" operator, but you can use
	       it directly.  The "qx/EXPR/" operator is	discussed in more de-
	       tail in "I/O Operators" in perlop.

       recv SOCKET,SCALAR,LENGTH,FLAGS
	       Receives	a message on a socket.	Attempts to receive LENGTH
	       characters of data into variable	SCALAR from the	specified
	       SOCKET filehandle.  SCALAR will be grown	or shrunk to the
	       length actually read.  Takes the	same flags as the system call
	       of the same name.  Returns the address of the sender if
	       SOCKET's	protocol supports this;	returns	an empty string	other-
	       wise.  If there's an error, returns the undefined value.	 This
	       call is actually	implemented in terms of	recvfrom(2) system
	       call.  See "UDP:	Message	Passing" in perlipc for	examples.

	       Note the	characters: depending on the status of the socket, ei-
	       ther (8-bit) bytes or characters	are received.  By default all
	       sockets operate on bytes, but for example if the	socket has
	       been changed using binmode() to operate with the	":encod-
	       ing(utf8)" I/O layer (see the "open" pragma, open), the I/O
	       will operate on UTF-8 encoded Unicode characters, not bytes.
	       Similarly for the ":encoding" pragma: in	that case pretty much
	       any characters can be read.

       redo LABEL
       redo    The "redo" command restarts the loop block without evaluating
	       the conditional again.  The "continue" block, if	any, is	not
	       executed.  If the LABEL is omitted, the command refers to the
	       innermost enclosing loop.  Programs that	want to	lie to them-
	       selves about what was just input	normally use this command:

		   # a simpleminded Pascal comment stripper
		   # (warning: assumes no { or } in strings)
		   LINE: while (<STDIN>) {
		       while (s|({.*}.*){.*}|$1	|) {}
		       s|{.*}| |;
		       if (s|{.*| |) {
			   $front = $_;
			   while (<STDIN>) {
			       if (/}/)	{      # end of	comment?
				   s|^|$front\{|;
				   redo	LINE;
			       }
			   }
		       }
		       print;
		   }

	       "redo" cannot be	used to	retry a	block which returns a value
	       such as "eval {}", "sub {}" or "do {}", and should not be used
	       to exit a grep()	or map() operation.

	       Note that a block by itself is semantically identical to	a loop
	       that executes once.  Thus "redo"	inside such a block will ef-
	       fectively turn it into a	looping	construct.

	       See also	"continue" for an illustration of how "last", "next",
	       and "redo" work.

       ref EXPR
       ref     Returns a non-empty string if EXPR is a reference, the empty
	       string otherwise. If EXPR is not	specified, $_ will be used.
	       The value returned depends on the type of thing the reference
	       is a reference to.  Builtin types include:

		   SCALAR
		   ARRAY
		   HASH
		   CODE
		   REF
		   GLOB
		   LVALUE
		   FORMAT
		   IO
		   Regexp

	       If the referenced object	has been blessed into a	package, then
	       that package name is returned instead.  You can think of	"ref"
	       as a "typeof" operator.

		   if (ref($r) eq "HASH") {
		       print "r	is a reference to a hash.\n";
		   }
		   unless (ref($r)) {
		       print "r	is not a reference at all.\n";
		   }

	       The return value	"LVALUE" indicates a reference to an lvalue
	       that is not a variable. You get this from taking	the reference
	       of function calls like "pos()" or "substr()".

	       The result "Regexp" indicates that the argument is a regular
	       expression resulting from "qr//".

	       See also	perlref.

       rename OLDNAME,NEWNAME
	       Changes the name	of a file; an existing file NEWNAME will be
	       clobbered.  Returns true	for success, false otherwise.

	       Behavior	of this	function varies	wildly depending on your sys-
	       tem implementation.  For	example, it will usually not work
	       across file system boundaries, even though the system mv	com-
	       mand sometimes compensates for this.  Other restrictions	in-
	       clude whether it	works on directories, open files, or pre-ex-
	       isting files.  Check perlport and either	the rename(2) manpage
	       or equivalent system documentation for details.

	       For a platform independent "move" function look at the
	       File::Copy module.

       require VERSION
       require EXPR
       require Demands a version of Perl specified by VERSION, or demands some
	       semantics specified by EXPR or by $_ if EXPR is not supplied.

	       VERSION may be either a numeric argument	such as	5.006, which
	       will be compared	to $], or a literal of the form	v5.6.1,	which
	       will be compared	to $^V (aka $PERL_VERSION).  A fatal error is
	       produced	at run time if VERSION is greater than the version of
	       the current Perl	interpreter.  Compare with "use", which	can do
	       a similar check at compile time.

	       Specifying VERSION as a literal of the form v5.6.1 should gen-
	       erally be avoided, because it leads to misleading error mes-
	       sages under earlier versions of Perl that do not	support	this
	       syntax.	The equivalent numeric version should be used instead.

		   require v5.6.1;     # run time version check
		   require 5.6.1;      # ditto
		   require 5.006_001;  # ditto;	preferred for backwards	compatibility

	       Otherwise, "require" demands that a library file	be included if
	       it hasn't already been included.	 The file is included via the
	       do-FILE mechanism, which	is essentially just a variety of
	       "eval" with the caveat that lexical variables in	the invoking
	       script will be invisible	to the included	code.  Has semantics
	       similar to the following	subroutine:

		   sub require {
		      my ($filename) = @_;
		      if (exists $INC{$filename}) {
			  return 1 if $INC{$filename};
			  die "Compilation failed in require";
		      }
		      my ($realfilename,$result);
		      ITER: {
			  foreach $prefix (@INC) {
			      $realfilename = "$prefix/$filename";
			      if (-f $realfilename) {
				  $INC{$filename} = $realfilename;
				  $result = do $realfilename;
				  last ITER;
			      }
			  }
			  die "Can't find $filename in \@INC";
		      }
		      if ($@) {
			  $INC{$filename} = undef;
			  die $@;
		      }	elsif (!$result) {
			  delete $INC{$filename};
			  die "$filename did not return	true value";
		      }	else {
			  return $result;
		      }
		   }

	       Note that the file will not be included twice under the same
	       specified name.

	       The file	must return true as the	last statement to indicate
	       successful execution of any initialization code,	so it's	cus-
	       tomary to end such a file with "1;" unless you're sure it'll
	       return true otherwise.  But it's	better just to put the "1;",
	       in case you add more statements.

	       If EXPR is a bareword, the require assumes a ".pm" extension
	       and replaces "::" with "/" in the filename for you, to make it
	       easy to load standard modules.  This form of loading of modules
	       does not	risk altering your namespace.

	       In other	words, if you try this:

		       require Foo::Bar;    # a	splendid bareword

	       The require function will actually look for the "Foo/Bar.pm"
	       file in the directories specified in the	@INC array.

	       But if you try this:

		       $class =	'Foo::Bar';
		       require $class;	    # $class is	not a bareword
		   #or
		       require "Foo::Bar";  # not a bareword because of	the ""

	       The require function will look for the "Foo::Bar" file in the
	       @INC array and will complain about not finding "Foo::Bar"
	       there.  In this case you	can do:

		       eval "require $class";

	       Now that	you understand how "require" looks for files in	the
	       case of a bareword argument, there is a little extra function-
	       ality going on behind the scenes.  Before "require" looks for a
	       ".pm" extension,	it will	first look for a filename with a
	       ".pmc" extension.  A file with this extension is	assumed	to be
	       Perl bytecode generated by B::Bytecode.	If this	file is	found,
	       and its modification time is newer than a coinciding ".pm" non-
	       compiled	file, it will be loaded	in place of that non-compiled
	       file ending in a	".pm" extension.

	       You can also insert hooks into the import facility, by putting
	       directly	Perl code into the @INC	array.	There are three	forms
	       of hooks: subroutine references,	array references and blessed
	       objects.

	       Subroutine references are the simplest case.  When the inclu-
	       sion system walks through @INC and encounters a subroutine,
	       this subroutine gets called with	two parameters,	the first be-
	       ing a reference to itself, and the second the name of the file
	       to be included (e.g. "Foo/Bar.pm").  The	subroutine should re-
	       turn nothing, or	a list of up to	three values in	the following
	       order:

	       1   A filehandle, from which the	file will be read.

	       2   A reference to a subroutine.	If there is no filehandle
		   (previous item), then this subroutine is expected to	gener-
		   ate one line	of source code per call, writing the line into
		   $_ and returning 1, then returning 0	at "end	of file". If
		   there is a filehandle, then the subroutine will be called
		   to act a simple source filter, with the line	as read	in $_.
		   Again, return 1 for each valid line,	and 0 after all	lines
		   have	been returned.

	       3   Optional state for the subroutine. The state	is passed in
		   as $_[1]. A reference to the	subroutine itself is passed in
		   as $_[0].

	       If an empty list, "undef", or nothing that matches the first 3
	       values above is returned	then "require" will look at the	re-
	       maining elements	of @INC.  Note that this file handle must be a
	       real file handle	(strictly a typeglob, or reference to a	type-
	       glob, blessed or	unblessed) - tied file handles will be ignored
	       and return value	processing will	stop there.

	       If the hook is an array reference, its first element must be a
	       subroutine reference.  This subroutine is called	as above, but
	       the first parameter is the array	reference.  This enables to
	       pass indirectly some arguments to the subroutine.

	       In other	words, you can write:

		   push	@INC, \&my_sub;
		   sub my_sub {
		       my ($coderef, $filename)	= @_;  # $coderef is \&my_sub
		       ...
		   }

	       or:

		   push	@INC, [	\&my_sub, $x, $y, ... ];
		   sub my_sub {
		       my ($arrayref, $filename) = @_;
		       # Retrieve $x, $y, ...
		       my @parameters =	@$arrayref[1..$#$arrayref];
		       ...
		   }

	       If the hook is an object, it must provide an INC	method that
	       will be called as above,	the first parameter being the object
	       itself.	(Note that you must fully qualify the sub's name, as
	       unqualified "INC" is always forced into package "main".)	 Here
	       is a typical code layout:

		   # In	Foo.pm
		   package Foo;
		   sub new { ... }
		   sub Foo::INC	{
		       my ($self, $filename) = @_;
		       ...
		   }

		   # In	the main program
		   push	@INC, new Foo(...);

	       Note that these hooks are also permitted	to set the %INC	entry
	       corresponding to	the files they have loaded. See	"%INC" in per-
	       lvar.

	       For a yet-more-powerful import facility,	see "use" and perlmod.

       reset EXPR
       reset   Generally used in a "continue" block at the end of a loop to
	       clear variables and reset "??" searches so that they work
	       again.  The expression is interpreted as	a list of single char-
	       acters (hyphens allowed for ranges).  All variables and arrays
	       beginning with one of those letters are reset to	their pristine
	       state.  If the expression is omitted, one-match searches
	       ("?pattern?") are reset to match	again.	Resets only variables
	       or searches in the current package.  Always returns 1.  Exam-
	       ples:

		   reset 'X';	       # reset all X variables
		   reset 'a-z';	       # reset lower case variables
		   reset;	       # just reset ?one-time? searches

	       Resetting "A-Z" is not recommended because you'll wipe out your
	       @ARGV and @INC arrays and your %ENV hash.  Resets only package
	       variables--lexical variables are	unaffected, but	they clean
	       themselves up on	scope exit anyway, so you'll probably want to
	       use them	instead.  See "my".

       return EXPR
       return  Returns from a subroutine, "eval", or "do FILE" with the	value
	       given in	EXPR.  Evaluation of EXPR may be in list, scalar, or
	       void context, depending on how the return value will be used,
	       and the context may vary	from one execution to the next (see
	       "wantarray").  If no EXPR is given, returns an empty list in
	       list context, the undefined value in scalar context, and	(of
	       course) nothing at all in a void	context.

	       (Note that in the absence of an explicit	"return", a subrou-
	       tine, eval, or do FILE will automatically return	the value of
	       the last	expression evaluated.)

       reverse LIST
	       In list context,	returns	a list value consisting	of the ele-
	       ments of	LIST in	the opposite order.  In	scalar context,	con-
	       catenates the elements of LIST and returns a string value with
	       all characters in the opposite order.

		   print join(", ", reverse "world", "Hello"); # Hello,	world

		   print scalar	reverse	"dlrow ,", "olleH";    # Hello,	world

	       Used without arguments in scalar	context, reverse() reverses
	       $_.

		   $_ =	"dlrow ,olleH";
		   print reverse;			       # No output, list context
		   print scalar	reverse;		       # Hello,	world

	       This operator is	also handy for inverting a hash, although
	       there are some caveats.	If a value is duplicated in the	origi-
	       nal hash, only one of those can be represented as a key in the
	       inverted	hash.  Also, this has to unwind	one hash and build a
	       whole new one, which may	take some time on a large hash,	such
	       as from a DBM file.

		   %by_name = reverse %by_address;     # Invert	the hash

       rewinddir DIRHANDLE
	       Sets the	current	position to the	beginning of the directory for
	       the "readdir" routine on	DIRHANDLE.

       rindex STR,SUBSTR,POSITION
       rindex STR,SUBSTR
	       Works just like index() except that it returns the position of
	       the last	occurrence of SUBSTR in	STR.  If POSITION is speci-
	       fied, returns the last occurrence beginning at or before	that
	       position.

       rmdir FILENAME
       rmdir   Deletes the directory specified by FILENAME if that directory
	       is empty.  If it	succeeds it returns true, otherwise it returns
	       false and sets $! (errno).  If FILENAME is omitted, uses	$_.

	       To remove a directory tree recursively ("rm -rf"	on unix) look
	       at the "rmtree" function	of the File::Path module.

       s///    The substitution	operator.  See perlop.

       scalar EXPR
	       Forces EXPR to be interpreted in	scalar context and returns the
	       value of	EXPR.

		   @counts = ( scalar @a, scalar @b, scalar @c );

	       There is	no equivalent operator to force	an expression to be
	       interpolated in list context because in practice, this is never
	       needed.	If you really wanted to	do so, however,	you could use
	       the construction	"@{[ (some expression) ]}", but	usually	a sim-
	       ple "(some expression)" suffices.

	       Because "scalar"	is unary operator, if you accidentally use for
	       EXPR a parenthesized list, this behaves as a scalar comma ex-
	       pression, evaluating all	but the	last element in	void context
	       and returning the final element evaluated in scalar context.
	       This is seldom what you want.

	       The following single statement:

		       print uc(scalar(&foo,$bar)),$baz;

	       is the moral equivalent of these	two:

		       &foo;
		       print(uc($bar),$baz);

	       See perlop for more details on unary operators and the comma
	       operator.

       seek FILEHANDLE,POSITION,WHENCE
	       Sets FILEHANDLE's position, just	like the "fseek" call of
	       "stdio".	 FILEHANDLE may	be an expression whose value gives the
	       name of the filehandle.	The values for WHENCE are 0 to set the
	       new position in bytes to	POSITION, 1 to set it to the current
	       position	plus POSITION, and 2 to	set it to EOF plus POSITION
	       (typically negative).  For WHENCE you may use the constants
	       "SEEK_SET", "SEEK_CUR", and "SEEK_END" (start of	the file, cur-
	       rent position, end of the file) from the	Fcntl module.  Returns
	       1 upon success, 0 otherwise.

	       Note the	in bytes: even if the filehandle has been set to oper-
	       ate on characters (for example by using the ":encoding(utf8)"
	       open layer), tell() will	return byte offsets, not character
	       offsets (because	implementing that would	render seek() and
	       tell() rather slow).

	       If you want to position file for	"sysread" or "syswrite", don't
	       use "seek"--buffering makes its effect on the file's system po-
	       sition unpredictable and	non-portable.  Use "sysseek" instead.

	       Due to the rules	and rigors of ANSI C, on some systems you have
	       to do a seek whenever you switch	between	reading	and writing.
	       Amongst other things, this may have the effect of calling
	       stdio's clearerr(3).  A WHENCE of 1 ("SEEK_CUR")	is useful for
	       not moving the file position:

		   seek(TEST,0,1);

	       This is also useful for applications emulating "tail -f".  Once
	       you hit EOF on your read, and then sleep	for a while, you might
	       have to stick in	a seek() to reset things.  The "seek" doesn't
	       change the current position, but	it does	clear the end-of-file
	       condition on the	handle,	so that	the next "<FILE>" makes	Perl
	       try again to read something.  We	hope.

	       If that doesn't work (some IO implementations are particularly
	       cantankerous), then you may need	something more like this:

		   for (;;) {
		       for ($curpos = tell(FILE); $_ = <FILE>;
			    $curpos = tell(FILE)) {
			   # search for	some stuff and put it into files
		       }
		       sleep($for_a_while);
		       seek(FILE, $curpos, 0);
		   }

       seekdir DIRHANDLE,POS
	       Sets the	current	position for the "readdir" routine on DIRHAN-
	       DLE.  POS must be a value returned by "telldir".	 "seekdir"
	       also has	the same caveats about possible	directory compaction
	       as the corresponding system library routine.

       select FILEHANDLE
       select  Returns the currently selected filehandle.  If FILEHANDLE is
	       supplied, sets the new current default filehandle for output.
	       This has	two effects: first, a "write" or a "print" without a
	       filehandle will default to this FILEHANDLE.  Second, references
	       to variables related to output will refer to this output	chan-
	       nel.  For example, if you have to set the top of	form format
	       for more	than one output	channel, you might do the following:

		   select(REPORT1);
		   $^ =	'report1_top';
		   select(REPORT2);
		   $^ =	'report2_top';

	       FILEHANDLE may be an expression whose value gives the name of
	       the actual filehandle.  Thus:

		   $oldfh = select(STDERR); $| = 1; select($oldfh);

	       Some programmers	may prefer to think of filehandles as objects
	       with methods, preferring	to write the last example as:

		   use IO::Handle;
		   STDERR->autoflush(1);

       select RBITS,WBITS,EBITS,TIMEOUT
	       This calls the select(2)	system call with the bit masks speci-
	       fied, which can be constructed using "fileno" and "vec",	along
	       these lines:

		   $rin	= $win = $ein =	'';
		   vec($rin,fileno(STDIN),1) = 1;
		   vec($win,fileno(STDOUT),1) =	1;
		   $ein	= $rin | $win;

	       If you want to select on	many filehandles you might wish	to
	       write a subroutine:

		   sub fhbits {
		       my(@fhlist) = split(' ',$_[0]);
		       my($bits);
		       for (@fhlist) {
			   vec($bits,fileno($_),1) = 1;
		       }
		       $bits;
		   }
		   $rin	= fhbits('STDIN	TTY SOCK');

	       The usual idiom is:

		   ($nfound,$timeleft) =
		     select($rout=$rin,	$wout=$win, $eout=$ein,	$timeout);

	       or to block until something becomes ready just do this

		   $nfound = select($rout=$rin,	$wout=$win, $eout=$ein,	undef);

	       Most systems do not bother to return anything useful in
	       $timeleft, so calling select() in scalar	context	just returns
	       $nfound.

	       Any of the bit masks can	also be	undef.	The timeout, if	speci-
	       fied, is	in seconds, which may be fractional.  Note: not	all
	       implementations are capable of returning	the $timeleft.	If
	       not, they always	return $timeleft equal to the supplied $time-
	       out.

	       You can effect a	sleep of 250 milliseconds this way:

		   select(undef, undef,	undef, 0.25);

	       Note that whether "select" gets restarted after signals (say,
	       SIGALRM)	is implementation-dependent.  See also perlport	for
	       notes on	the portability	of "select".

	       On error, "select" behaves like the select(2) system call : it
	       returns -1 and sets $!.

	       Note: on	some Unixes, the select(2) system call may report a
	       socket file descriptor as "ready	for reading", when actually no
	       data is available, thus a subsequent read blocks. It can	be
	       avoided using always the	O_NONBLOCK flag	on the socket. See se-
	       lect(2) and fcntl(2) for	further	details.

	       WARNING:	One should not attempt to mix buffered I/O (like
	       "read" or <FH>) with "select", except as	permitted by POSIX,
	       and even	then only on POSIX systems.  You have to use "sysread"
	       instead.

       semctl ID,SEMNUM,CMD,ARG
	       Calls the System	V IPC function "semctl".  You'll probably have
	       to say

		   use IPC::SysV;

	       first to	get the	correct	constant definitions.  If CMD is
	       IPC_STAT	or GETALL, then	ARG must be a variable that will hold
	       the returned semid_ds structure or semaphore value array.  Re-
	       turns like "ioctl": the undefined value for error, ""0 but
	       true"" for zero,	or the actual return value otherwise.  The ARG
	       must consist of a vector	of native short	integers, which	may be
	       created with "pack("s!",(0)x$nsem)".  See also "SysV IPC" in
	       perlipc,	"IPC::SysV", "IPC::Semaphore" documentation.

       semget KEY,NSEMS,FLAGS
	       Calls the System	V IPC function semget.	Returns	the semaphore
	       id, or the undefined value if there is an error.	 See also
	       "SysV IPC" in perlipc, "IPC::SysV", "IPC::SysV::Semaphore" doc-
	       umentation.

       semop KEY,OPSTRING
	       Calls the System	V IPC function semop to	perform	semaphore op-
	       erations	such as	signalling and waiting.	 OPSTRING must be a
	       packed array of semop structures.  Each semop structure can be
	       generated with "pack("s!3", $semnum, $semop, $semflag)".	 The
	       length of OPSTRING implies the number of	semaphore operations.
	       Returns true if successful, or false if there is	an error.  As
	       an example, the following code waits on semaphore $semnum of
	       semaphore id $semid:

		   $semop = pack("s!3",	$semnum, -1, 0);
		   die "Semaphore trouble: $!\n" unless	semop($semid, $semop);

	       To signal the semaphore,	replace	"-1" with 1.  See also "SysV
	       IPC" in perlipc,	"IPC::SysV", and "IPC::SysV::Semaphore"	docu-
	       mentation.

       send SOCKET,MSG,FLAGS,TO
       send SOCKET,MSG,FLAGS
	       Sends a message on a socket.  Attempts to send the scalar MSG
	       to the SOCKET filehandle.  Takes	the same flags as the system
	       call of the same	name.  On unconnected sockets you must specify
	       a destination to	send TO, in which case it does a C "sendto".
	       Returns the number of characters	sent, or the undefined value
	       if there	is an error.  The C system call	sendmsg(2) is cur-
	       rently unimplemented.  See "UDP:	Message	Passing" in perlipc
	       for examples.

	       Note the	characters: depending on the status of the socket, ei-
	       ther (8-bit) bytes or characters	are sent.  By default all
	       sockets operate on bytes, but for example if the	socket has
	       been changed using binmode() to operate with the	":encod-
	       ing(utf8)" I/O layer (see "open", or the	"open" pragma, open),
	       the I/O will operate on UTF-8 encoded Unicode characters, not
	       bytes.  Similarly for the ":encoding" pragma: in	that case
	       pretty much any characters can be sent.

       setpgrp PID,PGRP
	       Sets the	current	process	group for the specified	PID, 0 for the
	       current process.	 Will produce a	fatal error if used on a ma-
	       chine that doesn't implement POSIX setpgid(2) or	BSD setp-
	       grp(2).	If the arguments are omitted, it defaults to "0,0".
	       Note that the BSD 4.2 version of	"setpgrp" does not accept any
	       arguments, so only "setpgrp(0,0)" is portable.  See also
	       "POSIX::setsid()".

       setpriority WHICH,WHO,PRIORITY
	       Sets the	current	priority for a process,	a process group, or a
	       user.  (See setpriority(2).)  Will produce a fatal error	if
	       used on a machine that doesn't implement	setpriority(2).

       setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
	       Sets the	socket option requested.  Returns undefined if there
	       is an error.  Use integer constants provided by the "Socket"
	       module for LEVEL	and OPNAME.  Values for	LEVEL can also be ob-
	       tained from getprotobyname.  OPTVAL might either	be a packed
	       string or an integer.  An integer OPTVAL	is shorthand for
	       pack("i", OPTVAL).

	       An example disabling the	Nagle's	algorithm for a	socket:

		   use Socket qw(IPPROTO_TCP TCP_NODELAY);
		   setsockopt($socket, IPPROTO_TCP, TCP_NODELAY, 1);

       shift ARRAY
       shift   Shifts the first	value of the array off and returns it, short-
	       ening the array by 1 and	moving everything down.	 If there are
	       no elements in the array, returns the undefined value.  If AR-
	       RAY is omitted, shifts the @_ array within the lexical scope of
	       subroutines and formats,	and the	@ARGV array at file scopes or
	       within the lexical scopes established by	the "eval ''", "BEGIN
	       {}", "INIT {}", "CHECK {}", and "END {}"	constructs.

	       See also	"unshift", "push", and "pop".  "shift" and "unshift"
	       do the same thing to the	left end of an array that "pop"	and
	       "push" do to the	right end.

       shmctl ID,CMD,ARG
	       Calls the System	V IPC function shmctl.	You'll probably	have
	       to say

		   use IPC::SysV;

	       first to	get the	correct	constant definitions.  If CMD is
	       "IPC_STAT", then	ARG must be a variable that will hold the re-
	       turned "shmid_ds" structure.  Returns like ioctl: the undefined
	       value for error,	"0 but true" for zero, or the actual return
	       value otherwise.	 See also "SysV	IPC" in	perlipc	and
	       "IPC::SysV" documentation.

       shmget KEY,SIZE,FLAGS
	       Calls the System	V IPC function shmget.	Returns	the shared
	       memory segment id, or the undefined value if there is an	error.
	       See also	"SysV IPC" in perlipc and "IPC::SysV" documentation.

       shmread ID,VAR,POS,SIZE
       shmwrite	ID,STRING,POS,SIZE
	       Reads or	writes the System V shared memory segment ID starting
	       at position POS for size	SIZE by	attaching to it, copying
	       in/out, and detaching from it.  When reading, VAR must be a
	       variable	that will hold the data	read.  When writing, if	STRING
	       is too long, only SIZE bytes are	used; if STRING	is too short,
	       nulls are written to fill out SIZE bytes.  Return true if suc-
	       cessful,	or false if there is an	error.	shmread() taints the
	       variable. See also "SysV	IPC" in	perlipc, "IPC::SysV" documen-
	       tation, and the "IPC::Shareable"	module from CPAN.

       shutdown	SOCKET,HOW
	       Shuts down a socket connection in the manner indicated by HOW,
	       which has the same interpretation as in the system call of the
	       same name.

		   shutdown(SOCKET, 0);	   # I/we have stopped reading data
		   shutdown(SOCKET, 1);	   # I/we have stopped writing data
		   shutdown(SOCKET, 2);	   # I/we have stopped using this socket

	       This is useful with sockets when	you want to tell the other
	       side you're done	writing	but not	done reading, or vice versa.
	       It's also a more	insistent form of close	because	it also	dis-
	       ables the file descriptor in any	forked copies in other pro-
	       cesses.

	       Returns 1 for success. In the case of error, returns "undef" if
	       the first argument is not a valid filehandle, or	returns	0 and
	       sets $! for any other failure.

       sin EXPR
       sin     Returns the sine	of EXPR	(expressed in radians).	 If EXPR is
	       omitted,	returns	sine of	$_.

	       For the inverse sine operation, you may use the
	       "Math::Trig::asin" function, or use this	relation:

		   sub asin { atan2($_[0], sqrt(1 - $_[0] * $_[0])) }

       sleep EXPR
       sleep   Causes the script to sleep for EXPR seconds, or forever if no
	       EXPR.  Returns the number of seconds actually slept.

	       May be interrupted if the process receives a signal such	as
	       "SIGALRM".

		   eval	{
		       local $SIG{ALARM} = sub { die "Alarm!\n"	};
		       sleep;
		   };
		   die $@ unless $@ eq "Alarm!\n";

	       You probably cannot mix "alarm" and "sleep" calls, because
	       "sleep" is often	implemented using "alarm".

	       On some older systems, it may sleep up to a full	second less
	       than what you requested,	depending on how it counts seconds.
	       Most modern systems always sleep	the full amount.  They may ap-
	       pear to sleep longer than that, however,	because	your process
	       might not be scheduled right away in a busy multitasking	sys-
	       tem.

	       For delays of finer granularity than one	second,	the
	       Time::HiRes module (from	CPAN, and starting from	Perl 5.8 part
	       of the standard distribution) provides usleep().	 You may also
	       use Perl's four-argument	version	of select() leaving the	first
	       three arguments undefined, or you might be able to use the
	       "syscall" interface to access setitimer(2) if your system sup-
	       ports it. See perlfaq8 for details.

	       See also	the POSIX module's "pause" function.

       socket SOCKET,DOMAIN,TYPE,PROTOCOL
	       Opens a socket of the specified kind and	attaches it to file-
	       handle SOCKET.  DOMAIN, TYPE, and PROTOCOL are specified	the
	       same as for the system call of the same name.  You should "use
	       Socket" first to	get the	proper definitions imported.  See the
	       examples	in "Sockets: Client/Server Communication" in perlipc.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened	file descriptor, as determined
	       by the value of $^F.  See "$^F" in perlvar.

       socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
	       Creates an unnamed pair of sockets in the specified domain, of
	       the specified type.  DOMAIN, TYPE, and PROTOCOL are specified
	       the same	as for the system call of the same name.  If unimple-
	       mented, yields a	fatal error.  Returns true if successful.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened	file descriptors, as deter-
	       mined by	the value of $^F.  See "$^F" in	perlvar.

	       Some systems defined "pipe" in terms of "socketpair", in	which
	       a call to "pipe(Rdr, Wtr)" is essentially:

		   use Socket;
		   socketpair(Rdr, Wtr,	AF_UNIX, SOCK_STREAM, PF_UNSPEC);
		   shutdown(Rdr, 1);	    # no more writing for reader
		   shutdown(Wtr, 0);	    # no more reading for writer

	       See perlipc for an example of socketpair	use.  Perl 5.8 and
	       later will emulate socketpair using IP sockets to localhost if
	       your system implements sockets but not socketpair.

       sort SUBNAME LIST
       sort BLOCK LIST
       sort LIST
	       In list context,	this sorts the LIST and	returns	the sorted
	       list value.  In scalar context, the behaviour of	"sort()" is
	       undefined.

	       If SUBNAME or BLOCK is omitted, "sort"s in standard string com-
	       parison order.  If SUBNAME is specified,	it gives the name of a
	       subroutine that returns an integer less than, equal to, or
	       greater than 0, depending on how	the elements of	the list are
	       to be ordered.  (The "<=>" and "cmp" operators are extremely
	       useful in such routines.)  SUBNAME may be a scalar variable
	       name (unsubscripted), in	which case the value provides the name
	       of (or a	reference to) the actual subroutine to use.  In	place
	       of a SUBNAME, you can provide a BLOCK as	an anonymous, in-line
	       sort subroutine.

	       If the subroutine's prototype is	"($$)",	the elements to	be
	       compared	are passed by reference	in @_, as for a	normal subrou-
	       tine.  This is slower than unprototyped subroutines, where the
	       elements	to be compared are passed into the subroutine as the
	       package global variables	$a and $b (see example below).	Note
	       that in the latter case,	it is usually counter-productive to
	       declare $a and $b as lexicals.

	       The values to be	compared are always passed by reference	and
	       should not be modified.

	       You also	cannot exit out	of the sort block or subroutine	using
	       any of the loop control operators described in perlsyn or with
	       "goto".

	       When "use locale" is in effect, "sort LIST" sorts LIST accord-
	       ing to the current collation locale.  See perllocale.

	       sort() returns aliases into the original	list, much as a	for
	       loop's index variable aliases the list elements.	 That is, mod-
	       ifying an element of a list returned by sort() (for example, in
	       a "foreach", "map" or "grep") actually modifies the element in
	       the original list.  This	is usually something to	be avoided
	       when writing clear code.

	       Perl 5.6	and earlier used a quicksort algorithm to implement
	       sort.  That algorithm was not stable, and could go quadratic.
	       (A stable sort preserves	the input order	of elements that com-
	       pare equal.  Although quicksort's run time is O(NlogN) when av-
	       eraged over all arrays of length	N, the time can	be O(N**2),
	       quadratic behavior, for some inputs.)  In 5.7, the quicksort
	       implementation was replaced with	a stable mergesort algorithm
	       whose worst-case	behavior is O(NlogN).  But benchmarks indi-
	       cated that for some inputs, on some platforms, the original
	       quicksort was faster.  5.8 has a	sort pragma for	limited	con-
	       trol of the sort.  Its rather blunt control of the underlying
	       algorithm may not persist into future Perls, but	the ability to
	       characterize the	input or output	in implementation independent
	       ways quite probably will.  See sort.

	       Examples:

		   # sort lexically
		   @articles = sort @files;

		   # same thing, but with explicit sort	routine
		   @articles = sort {$a	cmp $b}	@files;

		   # now case-insensitively
		   @articles = sort {uc($a) cmp	uc($b)}	@files;

		   # same thing	in reversed order
		   @articles = sort {$b	cmp $a}	@files;

		   # sort numerically ascending
		   @articles = sort {$a	<=> $b}	@files;

		   # sort numerically descending
		   @articles = sort {$b	<=> $a}	@files;

		   # this sorts	the %age hash by value instead of key
		   # using an in-line function
		   @eldest = sort { $age{$b} <=> $age{$a} } keys %age;

		   # sort using	explicit subroutine name
		   sub byage {
		       $age{$a}	<=> $age{$b};  # presuming numeric
		   }
		   @sortedclass	= sort byage @class;

		   sub backwards { $b cmp $a }
		   @harry  = qw(dog cat	x Cain Abel);
		   @george = qw(gone chased yz Punished	Axed);
		   print sort @harry;
			   # prints AbelCaincatdogx
		   print sort backwards	@harry;
			   # prints xdogcatCainAbel
		   print sort @george, 'to', @harry;
			   # prints AbelAxedCainPunishedcatchaseddoggonetoxyz

		   # inefficiently sort	by descending numeric compare using
		   # the first integer after the first = sign, or the
		   # whole record case-insensitively otherwise

		   @new	= sort {
		       ($b =~ /=(\d+)/)[0] <=> ($a =~ /=(\d+)/)[0]
					   ||
				   uc($a)  cmp	uc($b)
		   } @old;

		   # same thing, but much more efficiently;
		   # we'll build auxiliary indices instead
		   # for speed
		   @nums = @caps = ();
		   for (@old) {
		       push @nums, /=(\d+)/;
		       push @caps, uc($_);
		   }

		   @new	= @old[	sort {
				       $nums[$b] <=> $nums[$a]
						||
				       $caps[$a] cmp $caps[$b]
				      }	0..$#old
			      ];

		   # same thing, but without any temps
		   @new	= map {	$_->[0]	}
			  sort { $b->[1] <=> $a->[1]
					  ||
				 $a->[2] cmp $b->[2]
			  } map	{ [$_, /=(\d+)/, uc($_)] } @old;

		   # using a prototype allows you to use any comparison	subroutine
		   # as	a sort subroutine (including other package's subroutines)
		   package other;
		   sub backwards ($$) {	$_[1] cmp $_[0]; }     # $a and	$b are not set here

		   package main;
		   @new	= sort other::backwards	@old;

		   # guarantee stability, regardless of	algorithm
		   use sort 'stable';
		   @new	= sort { substr($a, 3, 5) cmp substr($b, 3, 5) } @old;

		   # force use of mergesort (not portable outside Perl 5.8)
		   use sort '_mergesort';  # note discouraging _
		   @new	= sort { substr($a, 3, 5) cmp substr($b, 3, 5) } @old;

	       If you're using strict, you must	not declare $a and $b as lexi-
	       cals.  They are package globals.	 That means if you're in the
	       "main" package and type

		   @articles = sort {$b	<=> $a}	@files;

	       then $a and $b are $main::a and $main::b	(or $::a and $::b),
	       but if you're in	the "FooPack" package, it's the	same as	typing

		   @articles = sort {$FooPack::b <=> $FooPack::a} @files;

	       The comparison function is required to behave.  If it returns
	       inconsistent results (sometimes saying $x[1] is less than $x[2]
	       and sometimes saying the	opposite, for example) the results are
	       not well-defined.

	       Because "<=>" returns "undef" when either operand is "NaN"
	       (not-a-number), and because "sort" will trigger a fatal error
	       unless the result of a comparison is defined, when sorting with
	       a comparison function like "$a <=> $b", be careful about	lists
	       that might contain a "NaN".  The	following example takes	advan-
	       tage of the fact	that "NaN != NaN" to eliminate any "NaN"s from
	       the input.

		   @result = sort { $a <=> $b }	grep { $_ == $_	} @input;

       splice ARRAY,OFFSET,LENGTH,LIST
       splice ARRAY,OFFSET,LENGTH
       splice ARRAY,OFFSET
       splice ARRAY
	       Removes the elements designated by OFFSET and LENGTH from an
	       array, and replaces them	with the elements of LIST, if any.  In
	       list context, returns the elements removed from the array.  In
	       scalar context, returns the last	element	removed, or "undef" if
	       no elements are removed.	 The array grows or shrinks as neces-
	       sary.  If OFFSET	is negative then it starts that	far from the
	       end of the array.  If LENGTH is omitted,	removes	everything
	       from OFFSET onward.  If LENGTH is negative, removes the ele-
	       ments from OFFSET onward	except for -LENGTH elements at the end
	       of the array.  If both OFFSET and LENGTH	are omitted, removes
	       everything. If OFFSET is	past the end of	the array, perl	issues
	       a warning, and splices at the end of the	array.

	       The following equivalences hold (assuming "$[ ==	0 and $#a >=
	       $i" )

		   push(@a,$x,$y)      splice(@a,@a,0,$x,$y)
		   pop(@a)	       splice(@a,-1)
		   shift(@a)	       splice(@a,0,1)
		   unshift(@a,$x,$y)   splice(@a,0,0,$x,$y)
		   $a[$i] = $y	       splice(@a,$i,1,$y)

	       Example,	assuming array lengths are passed before arrays:

		   sub aeq {   # compare two list values
		       my(@a) =	splice(@_,0,shift);
		       my(@b) =	splice(@_,0,shift);
		       return 0	unless @a == @b;       # same len?
		       while (@a) {
			   return 0 if pop(@a) ne pop(@b);
		       }
		       return 1;
		   }
		   if (&aeq($len,@foo[1..$len],0+@bar,@bar)) { ... }

       split /PATTERN/,EXPR,LIMIT
       split /PATTERN/,EXPR
       split /PATTERN/
       split   Splits the string EXPR into a list of strings and returns that
	       list.  By default, empty	leading	fields are preserved, and
	       empty trailing ones are deleted.	 (If all fields	are empty,
	       they are	considered to be trailing.)

	       In scalar context, returns the number of	fields found and
	       splits into the @_ array.  Use of split in scalar context is
	       deprecated, however, because it clobbers	your subroutine	argu-
	       ments.

	       If EXPR is omitted, splits the $_ string.  If PATTERN is	also
	       omitted,	splits on whitespace (after skipping any leading
	       whitespace).  Anything matching PATTERN is taken	to be a	delim-
	       iter separating the fields.  (Note that the delimiter may be
	       longer than one character.)

	       If LIMIT	is specified and positive, it represents the maximum
	       number of fields	the EXPR will be split into, though the	actual
	       number of fields	returned depends on the	number of times	PAT-
	       TERN matches within EXPR.  If LIMIT is unspecified or zero,
	       trailing	null fields are	stripped (which	potential users	of
	       "pop" would do well to remember).  If LIMIT is negative,	it is
	       treated as if an	arbitrarily large LIMIT	had been specified.
	       Note that splitting an EXPR that	evaluates to the empty string
	       always returns the empty	list, regardless of the	LIMIT speci-
	       fied.

	       A pattern matching the null string (not to be confused with a
	       null pattern "//", which	is just	one member of the set of pat-
	       terns matching a	null string) will split	the value of EXPR into
	       separate	characters at each point it matches that way.  For ex-
	       ample:

		   print join(':', split(/ */, 'hi there')), "\n";

	       produces	the output 'h:i:t:h:e:r:e'.

	       As a special case for "split", using the	empty pattern "//"
	       specifically matches only the null string, and is not be	con-
	       fused with the regular use of "//" to mean "the last successful
	       pattern match".	So, for	"split", the following:

		   print join(':', split(//, 'hi there')), "\n";

	       produces	the output 'h:i: :t:h:e:r:e'.

	       Empty leading fields are	produced when there are	positive-width
	       matches at the beginning	of the string; a zero-width match at
	       the beginning of	the string does	not produce an empty field.
	       For example:

		  print	join(':', split(/(?=\w)/, 'hi there!'));

	       produces	the output 'h:i	:t:h:e:r:e!'. Empty trailing fields,
	       on the other hand, are produced when there is a match at	the
	       end of the string (and when LIMIT is given and is not 0), re-
	       gardless	of the length of the match.  For example:

		  print	join(':', split(//,   'hi there!', -1)), "\n";
		  print	join(':', split(/\W/, 'hi there!', -1)), "\n";

	       produce the output 'h:i:	:t:h:e:r:e:!:' and 'hi:there:',	re-
	       spectively, both	with an	empty trailing field.

	       The LIMIT parameter can be used to split	a line partially

		   ($login, $passwd, $remainder) = split(/:/, $_, 3);

	       When assigning to a list, if LIMIT is omitted, or zero, Perl
	       supplies	a LIMIT	one larger than	the number of variables	in the
	       list, to	avoid unnecessary work.	 For the list above LIMIT
	       would have been 4 by default.  In time critical applications it
	       behooves	you not	to split into more fields than you really
	       need.

	       If the PATTERN contains parentheses, additional list elements
	       are created from	each matching substring	in the delimiter.

		   split(/([,-])/, "1-10,20", 3);

	       produces	the list value

		   (1, '-', 10,	',', 20)

	       If you had the entire header of a normal	Unix email message in
	       $header,	you could split	it up into fields and their values
	       this way:

		   $header =~ s/\n\s+/ /g;  # fix continuation lines
		   %hdrs   =  (UNIX_FROM => split /^(\S*?):\s*/m, $header);

	       The pattern "/PATTERN/" may be replaced with an expression to
	       specify patterns	that vary at runtime.  (To do runtime compila-
	       tion only once, use "/$variable/o".)

	       As a special case, specifying a PATTERN of space	(' ') will
	       split on	white space just as "split" with no arguments does.
	       Thus, "split(' ')" can be used to emulate awk's default behav-
	       ior, whereas "split(/ /)" will give you as many null initial
	       fields as there are leading spaces.  A "split" on "/\s+/" is
	       like a "split(' ')" except that any leading whitespace produces
	       a null first field.  A "split" with no arguments	really does a
	       "split('	', $_)"	internally.

	       A PATTERN of "/^/" is treated as	if it were "/^/m", since it
	       isn't much use otherwise.

	       Example:

		   open(PASSWD,	'/etc/passwd');
		   while (<PASSWD>) {
		       chomp;
		       ($login,	$passwd, $uid, $gid,
			$gcos, $home, $shell) =	split(/:/);
		       #...
		   }

	       As with regular pattern matching, any capturing parentheses
	       that are	not matched in a "split()" will	be set to "undef" when
	       returned:

		   @fields = split /(A)|B/, "1A2B3";
		   # @fields is	(1, 'A', 2, undef, 3)

       sprintf FORMAT, LIST
	       Returns a string	formatted by the usual "printf"	conventions of
	       the C library function "sprintf".  See below for	more details
	       and see sprintf(3) or printf(3) on your system for an explana-
	       tion of the general principles.

	       For example:

		       # Format	number with up to 8 leading zeroes
		       $result = sprintf("%08d", $number);

		       # Round number to 3 digits after	decimal	point
		       $rounded	= sprintf("%.3f", $number);

	       Perl does its own "sprintf" formatting--it emulates the C func-
	       tion "sprintf", but it doesn't use it (except for floating-
	       point numbers, and even then only the standard modifiers	are
	       allowed).  As a result, any non-standard	extensions in your lo-
	       cal "sprintf" are not available from Perl.

	       Unlike "printf",	"sprintf" does not do what you probably	mean
	       when you	pass it	an array as your first argument. The array is
	       given scalar context, and instead of using the 0th element of
	       the array as the	format,	Perl will use the count	of elements in
	       the array as the	format,	which is almost	never useful.

	       Perl's "sprintf"	permits	the following universally-known	con-
	       versions:

		  %%   a percent sign
		  %c   a character with	the given number
		  %s   a string
		  %d   a signed	integer, in decimal
		  %u   an unsigned integer, in decimal
		  %o   an unsigned integer, in octal
		  %x   an unsigned integer, in hexadecimal
		  %e   a floating-point	number,	in scientific notation
		  %f   a floating-point	number,	in fixed decimal notation
		  %g   a floating-point	number,	in %e or %f notation

	       In addition, Perl permits the following widely-supported	con-
	       versions:

		  %X   like %x,	but using upper-case letters
		  %E   like %e,	but using an upper-case	"E"
		  %G   like %g,	but with an upper-case "E" (if applicable)
		  %b   an unsigned integer, in binary
		  %p   a pointer (outputs the Perl value's address in hexadecimal)
		  %n   special:	*stores* the number of characters output so far
		       into the	next variable in the parameter list

	       Finally,	for backward (and we do	mean "backward") compatibil-
	       ity, Perl permits these unnecessary but widely-supported	con-
	       versions:

		  %i   a synonym for %d
		  %D   a synonym for %ld
		  %U   a synonym for %lu
		  %O   a synonym for %lo
		  %F   a synonym for %f

	       Note that the number of exponent	digits in the scientific nota-
	       tion produced by	%e, %E,	%g and %G for numbers with the modulus
	       of the exponent less than 100 is	system-dependent: it may be
	       three or	less (zero-padded as necessary).  In other words, 1.23
	       times ten to the	99th may be either "1.23e99" or	"1.23e099".

	       Between the "%" and the format letter, you may specify a	number
	       of additional attributes	controlling the	interpretation of the
	       format.	In order, these	are:

	       format parameter	index
		   An explicit format parameter	index, such as "2$". By	de-
		   fault sprintf will format the next unused argument in the
		   list, but this allows you to	take the arguments out of or-
		   der,	e.g.:

		     printf '%2$d %1$d', 12, 34;      #	prints "34 12"
		     printf '%3$d %d %1$d', 1, 2, 3;  #	prints "3 1 1"

	       flags
		   one or more of:

		      space   prefix non-negative number with a	space
		      +	      prefix non-negative number with a	plus sign
		      -	      left-justify within the field
		      0	      use zeros, not spaces, to	right-justify
		      #	      prefix non-zero octal with "0", non-zero hex with	"0x"
			      or "0X", non-zero	binary with "0b"

		   For example:

		     printf '<%	d>',  12;   # prints "<	12>"
		     printf '<%+d>',  12;   # prints "<+12>"
		     printf '<%6s>',  12;   # prints "<	   12>"
		     printf '<%-6s>', 12;   # prints "<12    >"
		     printf '<%06s>', 12;   # prints "<000012>"
		     printf '<%#o>',  12;   # prints "<014>"
		     printf '<%#x>',  12;   # prints "<0xc>"
		     printf '<%#X>',  12;   # prints "<0XC>"
		     printf '<%#b>',  12;   # prints "<0b1100>"
		     printf '<%#B>',  12;   # prints "<0B1100>"

		   When	a space	and a plus sign	are given as the flags at
		   once, a plus	sign is	used to	prefix a positive number.

		     printf '<%+ d>', 12;   # prints "<+12>"
		     printf '<%	+d>', 12;   # prints "<+12>"

		   When	the # flag and a precision are given in	the %o conver-
		   sion, the precision is incremented if it's necessary	for
		   the leading "0".

		     printf '<%#.5o>', 012;	 # prints "<00012>"
		     printf '<%#.5o>', 012345;	 # prints "<012345>"
		     printf '<%#.0o>', 0;	 # prints "<0>"

	       vector flag
		   This	flag tells perl	to interpret the supplied string as a
		   vector of integers, one for each character in the string.
		   Perl	applies	the format to each integer in turn, then joins
		   the resulting strings with a	separator (a dot "." by	de-
		   fault). This	can be useful for displaying ordinal values of
		   characters in arbitrary strings:

		     printf "%vd", "AB\x{100}";		  # prints "65.66.256"
		     printf "version is	v%vd\n", $^V;	  # Perl's version

		   Put an asterisk "*" before the "v" to override the string
		   to use to separate the numbers:

		     printf "address is	%*vX\n", ":", $addr;   # IPv6 address
		     printf "bits are %0*v8b\n", " ", $bits;   # random	bitstring

		   You can also	explicitly specify the argument	number to use
		   for the join	string using e.g. "*2$v":

		     printf '%*4$vX %*4$vX %*4$vX', @addr[1..3], ":";	# 3 IPv6 addresses

	       (minimum) width
		   Arguments are usually formatted to be only as wide as re-
		   quired to display the given value. You can override the
		   width by putting a number here, or get the width from the
		   next	argument (with "*") or from a specified	argument (with
		   e.g.	"*2$"):

		     printf '<%s>', "a";       # prints	"<a>"
		     printf '<%6s>', "a";      # prints	"<     a>"
		     printf '<%*s>', 6,	"a";   # prints	"<     a>"
		     printf '<%*2$s>', "a", 6; # prints	"<     a>"
		     printf '<%2s>', "long";   # prints	"<long>" (does not truncate)

		   If a	field width obtained through "*" is negative, it has
		   the same effect as the "-" flag: left-justification.

	       precision, or maximum width
		   You can specify a precision (for numeric conversions) or a
		   maximum width (for string conversions) by specifying	a "."
		   followed by a number.  For floating point formats, with the
		   exception of	'g' and	'G', this specifies the	number of dec-
		   imal	places to show (the default being 6), e.g.:

		     # these examples are subject to system-specific variation
		     printf '<%f>', 1;	  # prints "<1.000000>"
		     printf '<%.1f>', 1;  # prints "<1.0>"
		     printf '<%.0f>', 1;  # prints "<1>"
		     printf '<%e>', 10;	  # prints "<1.000000e+01>"
		     printf '<%.1e>', 10; # prints "<1.0e+01>"

		   For 'g' and 'G', this specifies the maximum number of dig-
		   its to show,	including prior	to the decimal point as	well
		   as after it,	e.g.:

		     # these examples are subject to system-specific variation
		     printf '<%g>', 1;	      #	prints "<1>"
		     printf '<%.10g>', 1;     #	prints "<1>"
		     printf '<%g>', 100;      #	prints "<100>"
		     printf '<%.1g>', 100;    #	prints "<1e+02>"
		     printf '<%.2g>', 100.01; #	prints "<1e+02>"
		     printf '<%.5g>', 100.01; #	prints "<100.01>"
		     printf '<%.4g>', 100.01; #	prints "<100>"

		   For integer conversions, specifying a precision implies
		   that	the output of the number itself	should be zero-padded
		   to this width, where	the 0 flag is ignored:

		     printf '<%.6d>', 1;      #	prints "<000001>"
		     printf '<%+.6d>', 1;     #	prints "<+000001>"
		     printf '<%-10.6d>', 1;   #	prints "<000001	   >"
		     printf '<%10.6d>',	1;    #	prints "<    000001>"
		     printf '<%010.6d>', 1;   #	prints "<    000001>"
		     printf '<%+10.6d>', 1;   #	prints "<   +000001>"

		     printf '<%.6x>', 1;      #	prints "<000001>"
		     printf '<%#.6x>', 1;     #	prints "<0x000001>"
		     printf '<%-10.6x>', 1;   #	prints "<000001	   >"
		     printf '<%10.6x>',	1;    #	prints "<    000001>"
		     printf '<%010.6x>', 1;   #	prints "<    000001>"
		     printf '<%#10.6x>', 1;   #	prints "<  0x000001>"

		   For string conversions, specifying a	precision truncates
		   the string to fit in	the specified width:

		     printf '<%.5s>', "truncated";   # prints "<trunc>"
		     printf '<%10.5s>',	"truncated"; # prints "<     trunc>"

		   You can also	get the	precision from the next	argument using
		   ".*":

		     printf '<%.6x>', 1;       # prints	"<000001>"
		     printf '<%.*x>', 6, 1;    # prints	"<000001>"

		   If a	precision obtained through "*" is negative, it has the
		   same	effect as no precision.

		     printf '<%.*s>',  7, "string";   #	prints "<string>"
		     printf '<%.*s>',  3, "string";   #	prints "<str>"
		     printf '<%.*s>',  0, "string";   #	prints "<>"
		     printf '<%.*s>', -1, "string";   #	prints "<string>"

		     printf '<%.*d>',  1, 0;   # prints	"<0>"
		     printf '<%.*d>',  0, 0;   # prints	"<>"
		     printf '<%.*d>', -1, 0;   # prints	"<0>"

		   You cannot currently	get the	precision from a specified
		   number, but it is intended that this	will be	possible in
		   the future using e.g. ".*2$":

		     printf '<%.*2$x>',	1, 6;	# INVALID, but in future will print "<000001>"

	       size
		   For numeric conversions, you	can specify the	size to	inter-
		   pret	the number as using "l", "h", "V", "q",	"L", or	"ll".
		   For integer conversions ("d u o x X b i D U O"), numbers
		   are usually assumed to be whatever the default integer size
		   is on your platform (usually	32 or 64 bits),	but you	can
		   override this to use	instead	one of the standard C types,
		   as supported	by the compiler	used to	build Perl:

		      l		  interpret integer as C type "long" or	"unsigned long"
		      h		  interpret integer as C type "short" or "unsigned short"
		      q, L or ll  interpret integer as C type "long long", "unsigned long long".
				  or "quads" (typically	64-bit integers)

		   The last will produce errors	if Perl	does not understand
		   "quads" in your installation. (This requires	that either
		   the platform	natively supports quads	or Perl	was specifi-
		   cally compiled to support quads.) You can find out whether
		   your	Perl supports quads via	Config:

			   use Config;
			   ($Config{use64bitint} eq 'define' ||	$Config{longsize} >= 8)	&&
				   print "quads\n";

		   For floating	point conversions ("e f	g E F G"), numbers are
		   usually assumed to be the default floating point size on
		   your	platform (double or long double), but you can force
		   'long double' with "q", "L",	or "ll"	if your	platform sup-
		   ports them. You can find out	whether	your Perl supports
		   long	doubles	via Config:

			   use Config;
			   $Config{d_longdbl} eq 'define' && print "long doubles\n";

		   You can find	out whether Perl considers 'long double' to be
		   the default floating	point size to use on your platform via
		   Config:

			   use Config;
			   ($Config{uselongdouble} eq 'define')	&&
				   print "long doubles by default\n";

		   It can also be the case that	long doubles and doubles are
		   the same thing:

			   use Config;
			   ($Config{doublesize}	== $Config{longdblsize}) &&
				   print "doubles are long doubles\n";

		   The size specifier "V" has no effect	for Perl code, but it
		   is supported	for compatibility with XS code;	it means 'use
		   the standard	size for a Perl	integer	(or floating-point
		   number)', which is already the default for Perl code.

	       order of	arguments
		   Normally, sprintf takes the next unused argument as the
		   value to format for each format specification. If the for-
		   mat specification uses "*" to require additional arguments,
		   these are consumed from the argument	list in	the order in
		   which they appear in	the format specification before	the
		   value to format. Where an argument is specified using an
		   explicit index, this	does not affect	the normal order for
		   the arguments (even when the	explicitly specified index
		   would have been the next argument in	any case).

		   So:

		     printf '<%*.*s>', $a, $b, $c;

		   would use $a	for the	width, $b for the precision and	$c as
		   the value to	format,	while:

		     printf '<%*1$.*s>', $a, $b;

		   would use $a	for the	width and the precision, and $b	as the
		   value to format.

		   Here	are some more examples - beware	that when using	an ex-
		   plicit index, the "$" may need to be	escaped:

		     printf "%2\$d %d\n",    12, 34;		   # will print	"34 12\n"
		     printf "%2\$d %d %d\n", 12, 34;		   # will print	"34 12 34\n"
		     printf "%3\$d %d %d\n", 12, 34, 56;	   # will print	"56 12 34\n"
		     printf "%2\$*3\$d %d\n", 12, 34, 3;	   # will print	" 34 12\n"

	       If "use locale" is in effect, and POSIX::setlocale() has	been
	       called, the character used for the decimal separator in format-
	       ted floating point numbers is affected by the LC_NUMERIC	lo-
	       cale.  See perllocale and POSIX.

       sqrt EXPR
       sqrt    Return the square root of EXPR.	If EXPR	is omitted, returns
	       square root of $_.  Only	works on non-negative operands,	unless
	       you've loaded the standard Math::Complex	module.

		   use Math::Complex;
		   print sqrt(-2);    #	prints 1.4142135623731i

       srand EXPR
       srand   Sets the	random number seed for the "rand" operator.

	       The point of the	function is to "seed" the "rand" function so
	       that "rand" can produce a different sequence each time you run
	       your program.

	       If srand() is not called	explicitly, it is called implicitly at
	       the first use of	the "rand" operator.  However, this was	not
	       the case	in versions of Perl before 5.004, so if	your script
	       will run	under older Perl versions, it should call "srand".

	       Most programs won't even	call srand() at	all, except those that
	       need a cryptographically-strong starting	point rather than the
	       generally acceptable default, which is based on time of day,
	       process ID, and memory allocation, or the /dev/urandom device,
	       if available.

	       You can call srand($seed) with the same $seed to	reproduce the
	       same sequence from rand(), but this is usually reserved for
	       generating predictable results for testing or debugging.	 Oth-
	       erwise, don't call srand() more than once in your program.

	       Do not call srand() (i.e. without an argument) more than	once
	       in a script.  The internal state	of the random number generator
	       should contain more entropy than	can be provided	by any seed,
	       so calling srand() again	actually loses randomness.

	       Most implementations of "srand" take an integer and will
	       silently	truncate decimal numbers.  This	means "srand(42)" will
	       usually produce the same	results	as "srand(42.1)".  To be safe,
	       always pass "srand" an integer.

	       In versions of Perl prior to 5.004 the default seed was just
	       the current "time".  This isn't a particularly good seed, so
	       many old	programs supply	their own seed value (often "time ^
	       $$" or "time ^ ($$ + ($$	<< 15))"), but that isn't necessary
	       any more.

	       For cryptographic purposes, however, you	need something much
	       more random than	the default seed.  Checksumming	the compressed
	       output of one or	more rapidly changing operating	system status
	       programs	is the usual method.  For example:

		   srand (time ^ $$ ^ unpack "%L*", `ps	axww | gzip -f`);

	       If you're particularly concerned	with this, see the "Math::Tru-
	       lyRandom" module	in CPAN.

	       Frequently called programs (like	CGI scripts) that simply use

		   time	^ $$

	       for a seed can fall prey	to the mathematical property that

		   a^b == (a+1)^(b+1)

	       one-third of the	time.  So don't	do that.

       stat FILEHANDLE
       stat EXPR
       stat DIRHANDLE
       stat    Returns a 13-element list giving	the status info	for a file,
	       either the file opened via FILEHANDLE or	DIRHANDLE, or named by
	       EXPR.  If EXPR is omitted, it stats $_.	Returns	a null list if
	       the stat	fails.	Typically used as follows:

		   ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
		      $atime,$mtime,$ctime,$blksize,$blocks)
			  = stat($filename);

	       Not all fields are supported on all filesystem types.  Here are
	       the meanings of the fields:

		 0 dev	    device number of filesystem
		 1 ino	    inode number
		 2 mode	    file mode  (type and permissions)
		 3 nlink    number of (hard) links to the file
		 4 uid	    numeric user ID of file's owner
		 5 gid	    numeric group ID of	file's owner
		 6 rdev	    the	device identifier (special files only)
		 7 size	    total size of file,	in bytes
		 8 atime    last access	time in	seconds	since the epoch
		 9 mtime    last modify	time in	seconds	since the epoch
		10 ctime    inode change time in seconds since the epoch (*)
		11 blksize  preferred block size for file system I/O
		12 blocks   actual number of blocks allocated

	       (The epoch was at 00:00 January 1, 1970 GMT.)

	       (*) Not all fields are supported	on all filesystem types. No-
	       tably, the ctime	field is non-portable.	In particular, you
	       cannot expect it	to be a	"creation time", see "Files and
	       Filesystems" in perlport	for details.

	       If "stat" is passed the special filehandle consisting of	an un-
	       derline,	no stat	is done, but the current contents of the stat
	       structure from the last "stat", "lstat",	or filetest are	re-
	       turned.	Example:

		   if (-x $file	&& (($d) = stat(_)) && $d < 0) {
		       print "$file is executable NFS file\n";
		   }

	       (This works on machines only for	which the device number	is
	       negative	under NFS.)

	       Because the mode	contains both the file type and	its permis-
	       sions, you should mask off the file type	portion	and (s)printf
	       using a "%o" if you want	to see the real	permissions.

		   $mode = (stat($filename))[2];
		   printf "Permissions are %04o\n", $mode & 07777;

	       In scalar context, "stat" returns a boolean value indicating
	       success or failure, and,	if successful, sets the	information
	       associated with the special filehandle "_".

	       The File::stat module provides a	convenient, by-name access
	       mechanism:

		   use File::stat;
		   $sb = stat($filename);
		   printf "File	is %s, size is %s, perm	%04o, mtime %s\n",
		       $filename, $sb->size, $sb->mode & 07777,
		       scalar localtime	$sb->mtime;

	       You can import symbolic mode constants ("S_IF*")	and functions
	       ("S_IS*") from the Fcntl	module:

		   use Fcntl ':mode';

		   $mode = (stat($filename))[2];

		   $user_rwx	  = ($mode & S_IRWXU) >> 6;
		   $group_read	  = ($mode & S_IRGRP) >> 3;
		   $other_execute =  $mode & S_IXOTH;

		   printf "Permissions are %04o\n", S_IMODE($mode), "\n";

		   $is_setuid	  =  $mode & S_ISUID;
		   $is_directory  =  S_ISDIR($mode);

	       You could write the last	two using the "-u" and "-d" operators.
	       The commonly available "S_IF*" constants	are

		   # Permissions: read,	write, execute,	for user, group, others.

		   S_IRWXU S_IRUSR S_IWUSR S_IXUSR
		   S_IRWXG S_IRGRP S_IWGRP S_IXGRP
		   S_IRWXO S_IROTH S_IWOTH S_IXOTH

		   # Setuid/Setgid/Stickiness/SaveText.
		   # Note that the exact meaning of these is system dependent.

		   S_ISUID S_ISGID S_ISVTX S_ISTXT

		   # File types.  Not necessarily all are available on your system.

		   S_IFREG S_IFDIR S_IFLNK S_IFBLK S_IFCHR S_IFIFO S_IFSOCK S_IFWHT S_ENFMT

		   # The following are compatibility aliases for S_IRUSR, S_IWUSR, S_IXUSR.

		   S_IREAD S_IWRITE S_IEXEC

	       and the "S_IF*" functions are

		   S_IMODE($mode)      the part	of $mode containing the	permission bits
				       and the setuid/setgid/sticky bits

		   S_IFMT($mode)       the part	of $mode containing the	file type
				       which can be bit-anded with e.g.	S_IFREG
				       or with the following functions

		   # The operators -f, -d, -l, -b, -c, -p, and -S.

		   S_ISREG($mode) S_ISDIR($mode) S_ISLNK($mode)
		   S_ISBLK($mode) S_ISCHR($mode) S_ISFIFO($mode) S_ISSOCK($mode)

		   # No	direct -X operator counterpart,	but for	the first one
		   # the -g operator is	often equivalent.  The ENFMT stands for
		   # record flocking enforcement, a platform-dependent feature.

		   S_ISENFMT($mode) S_ISWHT($mode)

	       See your	native chmod(2)	and stat(2) documentation for more de-
	       tails about the "S_*" constants.	 To get	status info for	a sym-
	       bolic link instead of the target	file behind the	link, use the
	       "lstat" function.

       study SCALAR
       study   Takes extra time	to study SCALAR	($_ if unspecified) in antici-
	       pation of doing many pattern matches on the string before it is
	       next modified.  This may	or may not save	time, depending	on the
	       nature and number of patterns you are searching on, and on the
	       distribution of character frequencies in	the string to be
	       searched--you probably want to compare run times	with and with-
	       out it to see which runs	faster.	 Those loops that scan for
	       many short constant strings (including the constant parts of
	       more complex patterns) will benefit most.  You may have only
	       one "study" active at a time--if	you study a different scalar
	       the first is "unstudied".  (The way "study" works is this: a
	       linked list of every character in the string to be searched is
	       made, so	we know, for example, where all	the 'k'	characters
	       are.  From each search string, the rarest character is se-
	       lected, based on	some static frequency tables constructed from
	       some C programs and English text.  Only those places that con-
	       tain this "rarest" character are	examined.)

	       For example, here is a loop that	inserts	index producing	en-
	       tries before any	line containing	a certain pattern:

		   while (<>) {
		       study;
		       print ".IX foo\n"       if /\bfoo\b/;
		       print ".IX bar\n"       if /\bbar\b/;
		       print ".IX blurfl\n"    if /\bblurfl\b/;
		       # ...
		       print;
		   }

	       In searching for	"/\bfoo\b/", only those	locations in $_	that
	       contain "f" will	be looked at, because "f" is rarer than	"o".
	       In general, this	is a big win except in pathological cases.
	       The only	question is whether it saves you more time than	it
	       took to build the linked	list in	the first place.

	       Note that if you	have to	look for strings that you don't	know
	       till runtime, you can build an entire loop as a string and
	       "eval" that to avoid recompiling	all your patterns all the
	       time.  Together with undefining $/ to input entire files	as one
	       record, this can	be very	fast, often faster than	specialized
	       programs	like fgrep(1).	The following scans a list of files
	       (@files)	for a list of words (@words), and prints out the names
	       of those	files that contain a match:

		   $search = 'while (<>) { study;';
		   foreach $word (@words) {
		       $search .= "++\$seen{\$ARGV} if /\\b$word\\b/;\n";
		   }
		   $search .= "}";
		   @ARGV = @files;
		   undef $/;
		   eval	$search;	       # this screams
		   $/ =	"\n";	       # put back to normal input delimiter
		   foreach $file (sort keys(%seen)) {
		       print $file, "\n";
		   }

       sub NAME	BLOCK
       sub NAME	(PROTO)	BLOCK
       sub NAME	: ATTRS	BLOCK
       sub NAME	(PROTO)	: ATTRS	BLOCK
	       This is subroutine definition, not a real function per se.
	       Without a BLOCK it's just a forward declaration.	 Without a
	       NAME, it's an anonymous function	declaration, and does actually
	       return a	value: the CODE	ref of the closure you just created.

	       See perlsub and perlref for details about subroutines and ref-
	       erences,	and attributes and Attribute::Handlers for more	infor-
	       mation about attributes.

       substr EXPR,OFFSET,LENGTH,REPLACEMENT
       substr EXPR,OFFSET,LENGTH
       substr EXPR,OFFSET
	       Extracts	a substring out	of EXPR	and returns it.	 First charac-
	       ter is at offset	0, or whatever you've set $[ to	(but don't do
	       that).  If OFFSET is negative (or more precisely, less than
	       $[), starts that	far from the end of the	string.	 If LENGTH is
	       omitted,	returns	everything to the end of the string.  If
	       LENGTH is negative, leaves that many characters off the end of
	       the string.

		   my $s = "The	black cat climbed the green tree";
		   my $color  =	substr $s, 4, 5;       # black
		   my $middle =	substr $s, 4, -11;     # black cat climbed the
		   my $end    =	substr $s, 14;	       # climbed the green tree
		   my $tail   =	substr $s, -4;	       # tree
		   my $z      =	substr $s, -4, 2;      # tr

	       You can use the substr()	function as an lvalue, in which	case
	       EXPR must itself	be an lvalue.  If you assign something shorter
	       than LENGTH, the	string will shrink, and	if you assign some-
	       thing longer than LENGTH, the string will grow to accommodate
	       it.  To keep the	string the same	length you may need to pad or
	       chop your value using "sprintf".

	       If OFFSET and LENGTH specify a substring	that is	partly outside
	       the string, only	the part within	the string is returned.	 If
	       the substring is	beyond either end of the string, substr() re-
	       turns the undefined value and produces a	warning.  When used as
	       an lvalue, specifying a substring that is entirely outside the
	       string is a fatal error.	 Here's	an example showing the behav-
	       ior for boundary	cases:

		   my $name = 'fred';
		   substr($name, 4) = 'dy';	       # $name is now 'freddy'
		   my $null = substr $name, 6, 2;      # returns '' (no	warning)
		   my $oops = substr $name, 7;	       # returns undef,	with warning
		   substr($name, 7) = 'gap';	       # fatal error

	       An alternative to using substr()	as an lvalue is	to specify the
	       replacement string as the 4th argument.	This allows you	to re-
	       place parts of the EXPR and return what was there before	in one
	       operation, just as you can with splice().

		   my $s = "The	black cat climbed the green tree";
		   my $z = substr $s, 14, 7, "jumped from";    # climbed
		   # $s	is now "The black cat jumped from the green tree"

       symlink OLDFILE,NEWFILE
	       Creates a new filename symbolically linked to the old filename.
	       Returns 1 for success, 0	otherwise.  On systems that don't sup-
	       port symbolic links, produces a fatal error at run time.	 To
	       check for that, use eval:

		   $symlink_exists = eval { symlink("",""); 1 };

       syscall NUMBER, LIST
	       Calls the system	call specified as the first element of the
	       list, passing the remaining elements as arguments to the	system
	       call.  If unimplemented,	produces a fatal error.	 The arguments
	       are interpreted as follows: if a	given argument is numeric, the
	       argument	is passed as an	int.  If not, the pointer to the
	       string value is passed.	You are	responsible to make sure a
	       string is pre-extended long enough to receive any result	that
	       might be	written	into a string.	You can't use a	string literal
	       (or other read-only string) as an argument to "syscall" because
	       Perl has	to assume that any string pointer might	be written
	       through.	 If your integer arguments are not literals and	have
	       never been interpreted in a numeric context, you	may need to
	       add 0 to	them to	force them to look like	numbers.  This emu-
	       lates the "syswrite" function (or vice versa):

		   require 'syscall.ph';	       # may need to run h2ph
		   $s =	"hi there\n";
		   syscall(&SYS_write, fileno(STDOUT), $s, length $s);

	       Note that Perl supports passing of up to	only 14	arguments to
	       your system call, which in practice should usually suffice.

	       Syscall returns whatever	value returned by the system call it
	       calls.  If the system call fails, "syscall" returns "-1"	and
	       sets $! (errno).	 Note that some	system calls can legitimately
	       return "-1".  The proper	way to handle such calls is to assign
	       "$!=0;" before the call and check the value of $! if syscall
	       returns "-1".

	       There's a problem with "syscall(&SYS_pipe)": it returns the
	       file number of the read end of the pipe it creates.  There is
	       no way to retrieve the file number of the other end.  You can
	       avoid this problem by using "pipe" instead.

       sysopen FILEHANDLE,FILENAME,MODE
       sysopen FILEHANDLE,FILENAME,MODE,PERMS
	       Opens the file whose filename is	given by FILENAME, and asso-
	       ciates it with FILEHANDLE.  If FILEHANDLE is an expression, its
	       value is	used as	the name of the	real filehandle	wanted.	 This
	       function	calls the underlying operating system's	"open" func-
	       tion with the parameters	FILENAME, MODE,	PERMS.

	       The possible values and flag bits of the	MODE parameter are
	       system-dependent; they are available via	the standard module
	       "Fcntl".	 See the documentation of your operating system's
	       "open" to see which values and flag bits	are available.	You
	       may combine several flags using the "|"-operator.

	       Some of the most	common values are "O_RDONLY" for opening the
	       file in read-only mode, "O_WRONLY" for opening the file in
	       write-only mode,	and "O_RDWR" for opening the file in read-
	       write mode.

	       For historical reasons, some values work	on almost every	system
	       supported by perl: zero means read-only,	one means write-only,
	       and two means read/write.  We know that these values do not
	       work under OS/390 & VM/ESA Unix and on the Macintosh; you prob-
	       ably don't want to use them in new code.

	       If the file named by FILENAME does not exist and	the "open"
	       call creates it (typically because MODE includes	the "O_CREAT"
	       flag), then the value of	PERMS specifies	the permissions	of the
	       newly created file.  If you omit	the PERMS argument to
	       "sysopen", Perl uses the	octal value 0666.  These permission
	       values need to be in octal, and are modified by your process's
	       current "umask".

	       In many systems the "O_EXCL" flag is available for opening
	       files in	exclusive mode.	 This is not locking: exclusiveness
	       means here that if the file already exists, sysopen() fails.
	       "O_EXCL"	may not	work on	network	filesystems, and has no	effect
	       unless the "O_CREAT" flag is set	as well.  Setting
	       "O_CREAT|O_EXCL"	prevents the file from being opened if it is a
	       symbolic	link.  It does not protect against symbolic links in
	       the file's path.

	       Sometimes you may want to truncate an already-existing file.
	       This can	be done	using the "O_TRUNC" flag.  The behavior	of
	       "O_TRUNC" with "O_RDONLY" is undefined.

	       You should seldom if ever use 0644 as argument to "sysopen",
	       because that takes away the user's option to have a more	per-
	       missive umask.  Better to omit it.  See the perlfunc(1) entry
	       on "umask" for more on this.

	       Note that "sysopen" depends on the fdopen() C library function.
	       On many UNIX systems, fdopen() is known to fail when file de-
	       scriptors exceed	a certain value, typically 255.	If you need
	       more file descriptors than that,	consider rebuilding Perl to
	       use the "sfio" library, or perhaps using	the POSIX::open()
	       function.

	       See perlopentut for a kinder, gentler explanation of opening
	       files.

       sysread FILEHANDLE,SCALAR,LENGTH,OFFSET
       sysread FILEHANDLE,SCALAR,LENGTH
	       Attempts	to read	LENGTH bytes of	data into variable SCALAR from
	       the specified FILEHANDLE, using the system call read(2).	 It
	       bypasses	buffered IO, so	mixing this with other kinds of	reads,
	       "print",	"write", "seek", "tell", or "eof" can cause confusion
	       because the perlio or stdio layers usually buffers data.	 Re-
	       turns the number	of bytes actually read,	0 at end of file, or
	       undef if	there was an error (in the latter case $! is also
	       set).  SCALAR will be grown or shrunk so	that the last byte ac-
	       tually read is the last byte of the scalar after	the read.

	       An OFFSET may be	specified to place the read data at some place
	       in the string other than	the beginning.	A negative OFFSET
	       specifies placement at that many	characters counting backwards
	       from the	end of the string.  A positive OFFSET greater than the
	       length of SCALAR	results	in the string being padded to the re-
	       quired size with	"\0" bytes before the result of	the read is
	       appended.

	       There is	no syseof() function, which is ok, since eof() doesn't
	       work very well on device	files (like ttys) anyway.  Use sys-
	       read() and check	for a return value for 0 to decide whether
	       you're done.

	       Note that if the	filehandle has been marked as ":utf8" Unicode
	       characters are read instead of bytes (the LENGTH, OFFSET, and
	       the return value	of sysread() are in Unicode characters).  The
	       ":encoding(...)"	layer implicitly introduces the	":utf8"	layer.
	       See "binmode", "open", and the "open" pragma, open.

       sysseek FILEHANDLE,POSITION,WHENCE
	       Sets FILEHANDLE's system	position in bytes using	the system
	       call lseek(2).  FILEHANDLE may be an expression whose value
	       gives the name of the filehandle.  The values for WHENCE	are 0
	       to set the new position to POSITION, 1 to set the it to the
	       current position	plus POSITION, and 2 to	set it to EOF plus PO-
	       SITION (typically negative).

	       Note the	in bytes: even if the filehandle has been set to oper-
	       ate on characters (for example by using the ":encoding(utf8)"
	       I/O layer), tell() will return byte offsets, not	character off-
	       sets (because implementing that would render sysseek() very
	       slow).

	       sysseek() bypasses normal buffered IO, so mixing	this with
	       reads (other than "sysread", for	example	"<>" or	read())
	       "print",	"write", "seek", "tell", or "eof" may cause confusion.

	       For WHENCE, you may also	use the	constants "SEEK_SET",
	       "SEEK_CUR", and "SEEK_END" (start of the	file, current posi-
	       tion, end of the	file) from the Fcntl module.  Use of the con-
	       stants is also more portable than relying on 0, 1, and 2.  For
	       example to define a "systell" function:

		       use Fcntl 'SEEK_CUR';
		       sub systell { sysseek($_[0], 0, SEEK_CUR) }

	       Returns the new position, or the	undefined value	on failure.  A
	       position	of zero	is returned as the string "0 but true";	thus
	       "sysseek" returns true on success and false on failure, yet you
	       can still easily	determine the new position.

       system LIST
       system PROGRAM LIST
	       Does exactly the	same thing as "exec LIST", except that a fork
	       is done first, and the parent process waits for the child
	       process to complete.  Note that argument	processing varies de-
	       pending on the number of	arguments.  If there is	more than one
	       argument	in LIST, or if LIST is an array	with more than one
	       value, starts the program given by the first element of the
	       list with arguments given by the	rest of	the list.  If there is
	       only one	scalar argument, the argument is checked for shell
	       metacharacters, and if there are	any, the entire	argument is
	       passed to the system's command shell for	parsing	(this is
	       "/bin/sh	-c" on Unix platforms, but varies on other platforms).
	       If there	are no shell metacharacters in the argument, it	is
	       split into words	and passed directly to "execvp", which is more
	       efficient.

	       Beginning with v5.6.0, Perl will	attempt	to flush all files
	       opened for output before	any operation that may do a fork, but
	       this may	not be supported on some platforms (see	perlport).  To
	       be safe,	you may	need to	set $| ($AUTOFLUSH in English) or call
	       the "autoflush()" method	of "IO::Handle"	on any open handles.

	       The return value	is the exit status of the program as returned
	       by the "wait" call.  To get the actual exit value, shift	right
	       by eight	(see below). See also "exec".  This is not what	you
	       want to use to capture the output from a	command, for that you
	       should use merely backticks or "qx//", as described in
	       "`STRING`" in perlop.  Return value of -1 indicates a failure
	       to start	the program or an error	of the wait(2) system call
	       (inspect	$! for the reason).

	       Like "exec", "system" allows you	to lie to a program about its
	       name if you use the "system PROGRAM LIST" syntax.  Again, see
	       "exec".

	       Since "SIGINT" and "SIGQUIT" are	ignored	during the execution
	       of "system", if you expect your program to terminate on receipt
	       of these	signals	you will need to arrange to do so yourself
	       based on	the return value.

		   @args = ("command", "arg1", "arg2");
		   system(@args) == 0
			or die "system @args failed: $?"

	       You can check all the failure possibilities by inspecting $?
	       like this:

		   if ($? == -1) {
		       print "failed to	execute: $!\n";
		   }
		   elsif ($? & 127) {
		       printf "child died with signal %d, %s coredump\n",
			   ($? & 127),	($? & 128) ? 'with' : 'without';
		   }
		   else	{
		       printf "child exited with value %d\n", $? >> 8;
		   }

	       Alternatively you might inspect the value of "${^CHILD_ER-
	       ROR_NATIVE}" with the W*() calls	of the POSIX extension.

	       When the	arguments get executed via the system shell, results
	       and return codes	will be	subject	to its quirks and capabili-
	       ties.  See "`STRING`" in	perlop and "exec" for details.

       syswrite	FILEHANDLE,SCALAR,LENGTH,OFFSET
       syswrite	FILEHANDLE,SCALAR,LENGTH
       syswrite	FILEHANDLE,SCALAR
	       Attempts	to write LENGTH	bytes of data from variable SCALAR to
	       the specified FILEHANDLE, using the system call write(2).  If
	       LENGTH is not specified,	writes whole SCALAR.  It bypasses
	       buffered	IO, so mixing this with	reads (other than sysread()),
	       "print",	"write", "seek", "tell", or "eof" may cause confusion
	       because the perlio and stdio layers usually buffers data.  Re-
	       turns the number	of bytes actually written, or "undef" if there
	       was an error (in	this case the errno variable $!	is also	set).
	       If the LENGTH is	greater	than the available data	in the SCALAR
	       after the OFFSET, only as much data as is available will	be
	       written.

	       An OFFSET may be	specified to write the data from some part of
	       the string other	than the beginning.  A negative	OFFSET speci-
	       fies writing that many characters counting backwards from the
	       end of the string.  In the case the SCALAR is empty you can use
	       OFFSET but only zero offset.

	       Note that if the	filehandle has been marked as ":utf8", Unicode
	       characters are written instead of bytes (the LENGTH, OFFSET,
	       and the return value of syswrite() are in UTF-8 encoded Unicode
	       characters).  The ":encoding(...)" layer	implicitly introduces
	       the ":utf8" layer.  See "binmode", "open", and the "open"
	       pragma, open.

       tell FILEHANDLE
       tell    Returns the current position in bytes for FILEHANDLE, or	-1 on
	       error.  FILEHANDLE may be an expression whose value gives the
	       name of the actual filehandle.  If FILEHANDLE is	omitted, as-
	       sumes the file last read.

	       Note the	in bytes: even if the filehandle has been set to oper-
	       ate on characters (for example by using the ":encoding(utf8)"
	       open layer), tell() will	return byte offsets, not character
	       offsets (because	that would render seek() and tell() rather
	       slow).

	       The return value	of tell() for the standard streams like	the
	       STDIN depends on	the operating system: it may return -1 or
	       something else.	tell() on pipes, fifos,	and sockets usually
	       returns -1.

	       There is	no "systell" function.	Use "sysseek(FH, 0, 1)"	for
	       that.

	       Do not use tell() (or other buffered I/O	operations) on a file
	       handle that has been manipulated	by sysread(), syswrite() or
	       sysseek().  Those functions ignore the buffering, while tell()
	       does not.

       telldir DIRHANDLE
	       Returns the current position of the "readdir" routines on
	       DIRHANDLE.  Value may be	given to "seekdir" to access a partic-
	       ular location in	a directory.  "telldir"	has the	same caveats
	       about possible directory	compaction as the corresponding	system
	       library routine.

       tie VARIABLE,CLASSNAME,LIST
	       This function binds a variable to a package class that will
	       provide the implementation for the variable.  VARIABLE is the
	       name of the variable to be enchanted.  CLASSNAME	is the name of
	       a class implementing objects of correct type.  Any additional
	       arguments are passed to the "new" method	of the class (meaning
	       "TIESCALAR", "TIEHANDLE", "TIEARRAY", or	"TIEHASH").  Typically
	       these are arguments such	as might be passed to the "dbm_open()"
	       function	of C.  The object returned by the "new"	method is also
	       returned	by the "tie" function, which would be useful if	you
	       want to access other methods in CLASSNAME.

	       Note that functions such	as "keys" and "values" may return huge
	       lists when used on large	objects, like DBM files.  You may pre-
	       fer to use the "each" function to iterate over such.  Example:

		   # print out history file offsets
		   use NDBM_File;
		   tie(%HIST, 'NDBM_File', '/usr/lib/news/history', 1, 0);
		   while (($key,$val) =	each %HIST) {
		       print $key, ' = ', unpack('L',$val), "\n";
		   }
		   untie(%HIST);

	       A class implementing a hash should have the following methods:

		   TIEHASH classname, LIST
		   FETCH this, key
		   STORE this, key, value
		   DELETE this,	key
		   CLEAR this
		   EXISTS this,	key
		   FIRSTKEY this
		   NEXTKEY this, lastkey
		   SCALAR this
		   DESTROY this
		   UNTIE this

	       A class implementing an ordinary	array should have the follow-
	       ing methods:

		   TIEARRAY classname, LIST
		   FETCH this, key
		   STORE this, key, value
		   FETCHSIZE this
		   STORESIZE this, count
		   CLEAR this
		   PUSH	this, LIST
		   POP this
		   SHIFT this
		   UNSHIFT this, LIST
		   SPLICE this,	offset,	length,	LIST
		   EXTEND this,	count
		   DESTROY this
		   UNTIE this

	       A class implementing a file handle should have the following
	       methods:

		   TIEHANDLE classname,	LIST
		   READ	this, scalar, length, offset
		   READLINE this
		   GETC	this
		   WRITE this, scalar, length, offset
		   PRINT this, LIST
		   PRINTF this,	format,	LIST
		   BINMODE this
		   EOF this
		   FILENO this
		   SEEK	this, position,	whence
		   TELL	this
		   OPEN	this, mode, LIST
		   CLOSE this
		   DESTROY this
		   UNTIE this

	       A class implementing a scalar should have the following meth-
	       ods:

		   TIESCALAR classname,	LIST
		   FETCH this,
		   STORE this, value
		   DESTROY this
		   UNTIE this

	       Not all methods indicated above need be implemented.  See
	       perltie,	Tie::Hash, Tie::Array, Tie::Scalar, and	Tie::Handle.

	       Unlike "dbmopen", the "tie" function will not use or require a
	       module for you--you need	to do that explicitly yourself.	 See
	       DB_File or the Config module for	interesting "tie" implementa-
	       tions.

	       For further details see perltie,	"tied VARIABLE".

       tied VARIABLE
	       Returns a reference to the object underlying VARIABLE (the same
	       value that was originally returned by the "tie" call that bound
	       the variable to a package.)  Returns the	undefined value	if
	       VARIABLE	isn't tied to a	package.

       time    Returns the number of non-leap seconds since whatever time the
	       system considers	to be the epoch, suitable for feeding to "gm-
	       time" and "localtime". On most systems the epoch	is 00:00:00
	       UTC, January 1, 1970; a prominent exception being Mac OS	Clas-
	       sic which uses 00:00:00,	January	1, 1904	in the current local
	       time zone for its epoch.

	       For measuring time in better granularity	than one second, you
	       may use either the Time::HiRes module (from CPAN, and starting
	       from Perl 5.8 part of the standard distribution), or if you
	       have gettimeofday(2), you may be	able to	use the	"syscall" in-
	       terface of Perl.	 See perlfaq8 for details.

	       For date	and time processing look at the	many related modules
	       on CPAN.	 For a comprehensive date and time representation look
	       at the DateTime module.

       times   Returns a four-element list giving the user and system times,
	       in seconds, for this process and	the children of	this process.

		   ($user,$system,$cuser,$csystem) = times;

	       In scalar context, "times" returns $user.

	       Note that times for children are	included only after they ter-
	       minate.

       tr///   The transliteration operator.  Same as "y///".  See perlop.

       truncate	FILEHANDLE,LENGTH
       truncate	EXPR,LENGTH
	       Truncates the file opened on FILEHANDLE,	or named by EXPR, to
	       the specified length.  Produces a fatal error if	truncate isn't
	       implemented on your system.  Returns true if successful,	the
	       undefined value otherwise.

	       The behavior is undefined if LENGTH is greater than the length
	       of the file.

	       The position in the file	of FILEHANDLE is left unchanged.  You
	       may want	to call	seek before writing to the file.

       uc EXPR
       uc      Returns an uppercased version of	EXPR.  This is the internal
	       function	implementing the "\U" escape in	double-quoted strings.
	       Respects	current	LC_CTYPE locale	if "use	locale"	in force.  See
	       perllocale and perlunicode for more details about locale	and
	       Unicode support.	 It does not attempt to	do titlecase mapping
	       on initial letters.  See	"ucfirst" for that.

	       If EXPR is omitted, uses	$_.

       ucfirst EXPR
       ucfirst Returns the value of EXPR with the first	character in uppercase
	       (titlecase in Unicode).	This is	the internal function imple-
	       menting the "\u"	escape in double-quoted	strings.  Respects
	       current LC_CTYPE	locale if "use locale" in force.  See perllo-
	       cale and	perlunicode for	more details about locale and Unicode
	       support.

	       If EXPR is omitted, uses	$_.

       umask EXPR
       umask   Sets the	umask for the process to EXPR and returns the previous
	       value.  If EXPR is omitted, merely returns the current umask.

	       The Unix	permission "rwxr-x---" is represented as three sets of
	       three bits, or three octal digits: 0750 (the leading 0 indi-
	       cates octal and isn't one of the	digits).  The "umask" value is
	       such a number representing disabled permissions bits.  The per-
	       mission (or "mode") values you pass "mkdir" or "sysopen"	are
	       modified	by your	umask, so even if you tell "sysopen" to	create
	       a file with permissions 0777, if	your umask is 0022 then	the
	       file will actually be created with permissions 0755.  If	your
	       "umask" were 0027 (group	can't write; others can't read,	write,
	       or execute), then passing "sysopen" 0666	would create a file
	       with mode 0640 ("0666 &~	027" is	0640).

	       Here's some advice: supply a creation mode of 0666 for regular
	       files (in "sysopen") and	one of 0777 for	directories (in
	       "mkdir")	and executable files.  This gives users	the freedom of
	       choice: if they want protected files, they might	choose process
	       umasks of 022, 027, or even the particularly antisocial mask of
	       077.  Programs should rarely if ever make policy	decisions bet-
	       ter left	to the user.  The exception to this is when writing
	       files that should be kept private: mail files, web browser
	       cookies,	.rhosts	files, and so on.

	       If umask(2) is not implemented on your system and you are try-
	       ing to restrict access for yourself (i.e., (EXPR	& 0700)	> 0),
	       produces	a fatal	error at run time.  If umask(2)	is not imple-
	       mented and you are not trying to	restrict access	for yourself,
	       returns "undef".

	       Remember	that a umask is	a number, usually given	in octal; it
	       is not a	string of octal	digits.	 See also "oct", if all	you
	       have is a string.

       undef EXPR
       undef   Undefines the value of EXPR, which must be an lvalue.  Use only
	       on a scalar value, an array (using "@"),	a hash (using "%"), a
	       subroutine (using "&"), or a typeglob (using "*").  (Saying
	       "undef $hash{$key}" will	probably not do	what you expect	on
	       most predefined variables or DBM	list values, so	don't do that;
	       see delete.)  Always returns the	undefined value.  You can omit
	       the EXPR, in which case nothing is undefined, but you still get
	       an undefined value that you could, for instance,	return from a
	       subroutine, assign to a variable	or pass	as a parameter.	 Exam-
	       ples:

		   undef $foo;
		   undef $bar{'blurfl'};      #	Compare	to: delete $bar{'blurfl'};
		   undef @ary;
		   undef %hash;
		   undef &mysub;
		   undef *xyz;	     # destroys	$xyz, @xyz, %xyz, &xyz,	etc.
		   return (wantarray ? (undef, $errmsg)	: undef) if $they_blew_it;
		   select undef, undef,	undef, 0.25;
		   ($a,	$b, undef, $c) = &foo;	     # Ignore third value returned

	       Note that this is a unary operator, not a list operator.

       unlink LIST
       unlink  Deletes a list of files.	 Returns the number of files success-
	       fully deleted.

		   $cnt	= unlink 'a', 'b', 'c';
		   unlink @goners;
		   unlink <*.bak>;

	       Note: "unlink" will not attempt to delete directories unless
	       you are superuser and the -U flag is supplied to	Perl.  Even if
	       these conditions	are met, be warned that	unlinking a directory
	       can inflict damage on your filesystem.  Finally,	using "unlink"
	       on directories is not supported on many operating systems.  Use
	       "rmdir" instead.

	       If LIST is omitted, uses	$_.

       unpack TEMPLATE,EXPR
	       "unpack"	does the reverse of "pack": it takes a string and ex-
	       pands it	out into a list	of values.  (In	scalar context,	it re-
	       turns merely the	first value produced.)

	       The string is broken into chunks	described by the TEMPLATE.
	       Each chunk is converted separately to a value.  Typically, ei-
	       ther the	string is a result of "pack", or the characters	of the
	       string represent	a C structure of some kind.

	       The TEMPLATE has	the same format	as in the "pack" function.
	       Here's a	subroutine that	does substring:

		   sub substr {
		       my($what,$where,$howmuch) = @_;
		       unpack("x$where a$howmuch", $what);
		   }

	       and then	there's

		   sub ordinal { unpack("C",$_[0]); } #	same as	ord()

	       In addition to fields allowed in	pack(),	you may	prefix a field
	       with a %<number>	to indicate that you want a <number>-bit
	       checksum	of the items instead of	the items themselves.  Default
	       is a 16-bit checksum.  Checksum is calculated by	summing	nu-
	       meric values of expanded	values (for string fields the sum of
	       "ord($char)" is taken, for bit fields the sum of	zeroes and
	       ones).

	       For example, the	following computes the same number as the Sys-
	       tem V sum program:

		   $checksum = do {
		       local $/;  # slurp!
		       unpack("%32W*",<>) % 65535;
		   };

	       The following efficiently counts	the number of set bits in a
	       bit vector:

		   $setbits = unpack("%32b*", $selectmask);

	       The "p" and "P" formats should be used with care.  Since	Perl
	       has no way of checking whether the value	passed to "unpack()"
	       corresponds to a	valid memory location, passing a pointer value
	       that's not known	to be valid is likely to have disastrous con-
	       sequences.

	       If there	are more pack codes or if the repeat count of a	field
	       or a group is larger than what the remainder of the input
	       string allows, the result is not	well defined: in some cases,
	       the repeat count	is decreased, or "unpack()" will produce null
	       strings or zeroes, or terminate with an error. If the input
	       string is longer	than one described by the TEMPLATE, the	rest
	       is ignored.

	       See "pack" for more examples and	notes.

       untie VARIABLE
	       Breaks the binding between a variable and a package.  (See
	       "tie".)	Has no effect if the variable is not tied.

       unshift ARRAY,LIST
	       Does the	opposite of a "shift".	Or the opposite	of a "push",
	       depending on how	you look at it.	 Prepends list to the front of
	       the array, and returns the new number of	elements in the	array.

		   unshift(@ARGV, '-e')	unless $ARGV[0]	=~ /^-/;

	       Note the	LIST is	prepended whole, not one element at a time, so
	       the prepended elements stay in the same order.  Use "reverse"
	       to do the reverse.

       use Module VERSION LIST
       use Module VERSION
       use Module LIST
       use Module
       use VERSION
	       Imports some semantics into the current package from the	named
	       module, generally by aliasing certain subroutine	or variable
	       names into your package.	 It is exactly equivalent to

		   BEGIN { require Module; Module->import( LIST	); }

	       except that Module must be a bareword.

	       VERSION may be either a numeric argument	such as	5.006, which
	       will be compared	to $], or a literal of the form	v5.6.1,	which
	       will be compared	to $^V (aka $PERL_VERSION.  A fatal error is
	       produced	if VERSION is greater than the version of the current
	       Perl interpreter; Perl will not attempt to parse	the rest of
	       the file.  Compare with "require", which	can do a similar check
	       at run time.

	       Specifying VERSION as a literal of the form v5.6.1 should gen-
	       erally be avoided, because it leads to misleading error mes-
	       sages under earlier versions of Perl that do not	support	this
	       syntax.	The equivalent numeric version should be used instead.

		   use v5.6.1;	       # compile time version check
		   use 5.6.1;	       # ditto
		   use 5.006_001;      # ditto;	preferred for backwards	compatibility

	       This is often useful if you need	to check the current Perl ver-
	       sion before "use"ing library modules that have changed in in-
	       compatible ways from older versions of Perl.  (We try not to do
	       this more than we have to.)

	       The "BEGIN" forces the "require"	and "import" to	happen at com-
	       pile time.  The "require" makes sure the	module is loaded into
	       memory if it hasn't been	yet.  The "import" is not a
	       builtin--it's just an ordinary static method call into the
	       "Module"	package	to tell	the module to import the list of fea-
	       tures back into the current package.  The module	can implement
	       its "import" method any way it likes, though most modules just
	       choose to derive	their "import" method via inheritance from the
	       "Exporter" class	that is	defined	in the "Exporter" module.  See
	       Exporter.  If no	"import" method	can be found then the call is
	       skipped.

	       If you do not want to call the package's	"import" method	(for
	       instance, to stop your namespace	from being altered), explic-
	       itly supply the empty list:

		   use Module ();

	       That is exactly equivalent to

		   BEGIN { require Module }

	       If the VERSION argument is present between Module and LIST,
	       then the	"use" will call	the VERSION method in class Module
	       with the	given version as an argument.  The default VERSION
	       method, inherited from the UNIVERSAL class, croaks if the given
	       version is larger than the value	of the variable	$Module::VER-
	       SION.

	       Again, there is a distinction between omitting LIST ("import"
	       called with no arguments) and an	explicit empty LIST "()" ("im-
	       port" not called).  Note	that there is no comma after VERSION!

	       Because this is a wide-open interface, pragmas (compiler	direc-
	       tives) are also implemented this	way.  Currently	implemented
	       pragmas are:

		   use constant;
		   use diagnostics;
		   use integer;
		   use sigtrap	qw(SEGV	BUS);
		   use strict	qw(subs	vars refs);
		   use subs	qw(afunc blurfl);
		   use warnings	qw(all);
		   use sort	qw(stable _quicksort _mergesort);

	       Some of these pseudo-modules import semantics into the current
	       block scope (like "strict" or "integer",	unlike ordinary	mod-
	       ules, which import symbols into the current package (which are
	       effective through the end of the	file).

	       There's a corresponding "no" command that unimports meanings
	       imported	by "use", i.e.,	it calls "unimport Module LIST"	in-
	       stead of	"import".

		   no integer;
		   no strict 'refs';
		   no warnings;

	       See perlmodlib for a list of standard modules and pragmas.  See
	       perlrun for the "-M" and	"-m" command-line options to perl that
	       give "use" functionality	from the command-line.

       utime LIST
	       Changes the access and modification times on each file of a
	       list of files.  The first two elements of the list must be the
	       NUMERICAL access	and modification times,	in that	order.	Re-
	       turns the number	of files successfully changed.	The inode
	       change time of each file	is set to the current time.  For exam-
	       ple, this code has the same effect as the Unix touch(1) command
	       when the	files already exist and	belong to the user running the
	       program:

		   #!/usr/bin/perl
		   $atime = $mtime = time;
		   utime $atime, $mtime, @ARGV;

	       Since perl 5.7.2, if the	first two elements of the list are
	       "undef",	then the utime(2) function in the C library will be
	       called with a null second argument. On most systems, this will
	       set the file's access and modification times to the current
	       time (i.e. equivalent to	the example above) and will even work
	       on other	users' files where you have write permission:

		   utime undef,	undef, @ARGV;

	       Under NFS this will use the time	of the NFS server, not the
	       time of the local machine.  If there is a time synchronization
	       problem,	the NFS	server and local machine will have different
	       times.  The Unix	touch(1) command will in fact normally use
	       this form instead of the	one shown in the first example.

	       Note that only passing one of the first two elements as "undef"
	       will be equivalent of passing it	as 0 and will not have the
	       same effect as described	when they are both "undef".  This case
	       will also trigger an uninitialized warning.

	       On systems that support futimes,	you might pass file handles
	       among the files.	 On systems that don't support futimes,	pass-
	       ing file	handles	produces a fatal error at run time.  The file
	       handles must be passed as globs or references to	be recognized.
	       Barewords are considered	file names.

       values HASH
	       Returns a list consisting of all	the values of the named	hash.
	       (In a scalar context, returns the number	of values.)

	       The values are returned in an apparently	random order.  The ac-
	       tual random order is subject to change in future	versions of
	       perl, but it is guaranteed to be	the same order as either the
	       "keys" or "each"	function would produce on the same (unmodi-
	       fied) hash.  Since Perl 5.8.1 the ordering is different even
	       between different runs of Perl for security reasons (see	"Algo-
	       rithmic Complexity Attacks" in perlsec).

	       As a side effect, calling values() resets the HASH's internal
	       iterator, see "each". (In particular, calling values() in void
	       context resets the iterator with	no other overhead.)

	       Note that the values are	not copied, which means	modifying them
	       will modify the contents	of the hash:

		   for (values %hash)	   { s/foo/bar/g }   # modifies	%hash values
		   for (@hash{keys %hash}) { s/foo/bar/g }   # same

	       See also	"keys",	"each",	and "sort".

       vec EXPR,OFFSET,BITS
	       Treats the string in EXPR as a bit vector made up of elements
	       of width	BITS, and returns the value of the element specified
	       by OFFSET as an unsigned	integer.  BITS therefore specifies the
	       number of bits that are reserved	for each element in the	bit
	       vector.	This must be a power of	two from 1 to 32 (or 64, if
	       your platform supports that).

	       If BITS is 8, "elements"	coincide with bytes of the input
	       string.

	       If BITS is 16 or	more, bytes of the input string	are grouped
	       into chunks of size BITS/8, and each group is converted to a
	       number as with pack()/unpack() with big-endian formats "n"/"N"
	       (and analogously	for BITS==64).	See "pack" for details.

	       If bits is 4 or less, the string	is broken into bytes, then the
	       bits of each byte are broken into 8/BITS	groups.	 Bits of a
	       byte are	numbered in a little-endian-ish	way, as	in 0x01, 0x02,
	       0x04, 0x08, 0x10, 0x20, 0x40, 0x80.  For	example, breaking the
	       single input byte "chr(0x36)" into two groups gives a list
	       "(0x6, 0x3)"; breaking it into 4	groups gives "(0x2, 0x1, 0x3,
	       0x0)".

	       "vec" may also be assigned to, in which case parentheses	are
	       needed to give the expression the correct precedence as in

		   vec($image, $max_x *	$x + $y, 8) = 3;

	       If the selected element is outside the string, the value	0 is
	       returned.  If an	element	off the	end of the string is written
	       to, Perl	will first extend the string with sufficiently many
	       zero bytes.   It	is an error to try to write off	the beginning
	       of the string (i.e. negative OFFSET).

	       If the string happens to	be encoded as UTF-8 internally (and
	       thus has	the UTF8 flag set), this is ignored by "vec", and it
	       operates	on the internal	byte string, not the conceptual	char-
	       acter string, even if you only have characters with values less
	       than 256.

	       Strings created with "vec" can also be manipulated with the
	       logical operators "|", "&", "^",	and "~".  These	operators will
	       assume a	bit vector operation is	desired	when both operands are
	       strings.	 See "Bitwise String Operators"	in perlop.

	       The following code will build up	an ASCII string	saying
	       'PerlPerlPerl'.	The comments show the string after each	step.
	       Note that this code works in the	same way on big-endian or lit-
	       tle-endian machines.

		   my $foo = '';
		   vec($foo,  0, 32) = 0x5065726C;     # 'Perl'

		   # $foo eq "Perl" eq "\x50\x65\x72\x6C", 32 bits
		   print vec($foo, 0, 8);	       # prints	80 == 0x50 == ord('P')

		   vec($foo,  2, 16) = 0x5065;	       # 'PerlPe'
		   vec($foo,  3, 16) = 0x726C;	       # 'PerlPerl'
		   vec($foo,  8,  8) = 0x50;	       # 'PerlPerlP'
		   vec($foo,  9,  8) = 0x65;	       # 'PerlPerlPe'
		   vec($foo, 20,  4) = 2;	       # 'PerlPerlPe'	. "\x02"
		   vec($foo, 21,  4) = 7;	       # 'PerlPerlPer'
						       # 'r' is	"\x72"
		   vec($foo, 45,  2) = 3;	       # 'PerlPerlPer'	. "\x0c"
		   vec($foo, 93,  1) = 1;	       # 'PerlPerlPer'	. "\x2c"
		   vec($foo, 94,  1) = 1;	       # 'PerlPerlPerl'
						       # 'l' is	"\x6c"

	       To transform a bit vector into a	string or list of 0's and 1's,
	       use these:

		   $bits = unpack("b*",	$vector);
		   @bits = split(//, unpack("b*", $vector));

	       If you know the exact length in bits, it	can be used in place
	       of the "*".

	       Here is an example to illustrate	how the	bits actually fall in
	       place:

		   #!/usr/bin/perl -wl

		   print <<'EOT';
						     0	       1	 2	   3
				      unpack("V",$_) 01234567890123456789012345678901
		   ------------------------------------------------------------------
		   EOT

		   for $w (0..3) {
		       $width =	2**$w;
		       for ($shift=0; $shift < $width; ++$shift) {
			   for ($off=0;	$off < 32/$width; ++$off) {
			       $str = pack("B*", "0"x32);
			       $bits = (1<<$shift);
			       vec($str, $off, $width) = $bits;
			       $res = unpack("b*",$str);
			       $val = unpack("V", $str);
			       write;
			   }
		       }
		   }

		   format STDOUT =
		   vec($_,@#,@#) = @<< == @######### @>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
		   $off, $width, $bits,	$val, $res
		   .
		   __END__

	       Regardless of the machine architecture on which it is run, the
	       above example should print the following	table:

						     0	       1	 2	   3
				      unpack("V",$_) 01234567890123456789012345678901
		   ------------------------------------------------------------------
		   vec($_, 0, 1) = 1   ==	   1 10000000000000000000000000000000
		   vec($_, 1, 1) = 1   ==	   2 01000000000000000000000000000000
		   vec($_, 2, 1) = 1   ==	   4 00100000000000000000000000000000
		   vec($_, 3, 1) = 1   ==	   8 00010000000000000000000000000000
		   vec($_, 4, 1) = 1   ==	  16 00001000000000000000000000000000
		   vec($_, 5, 1) = 1   ==	  32 00000100000000000000000000000000
		   vec($_, 6, 1) = 1   ==	  64 00000010000000000000000000000000
		   vec($_, 7, 1) = 1   ==	 128 00000001000000000000000000000000
		   vec($_, 8, 1) = 1   ==	 256 00000000100000000000000000000000
		   vec($_, 9, 1) = 1   ==	 512 00000000010000000000000000000000
		   vec($_,10, 1) = 1   ==	1024 00000000001000000000000000000000
		   vec($_,11, 1) = 1   ==	2048 00000000000100000000000000000000
		   vec($_,12, 1) = 1   ==	4096 00000000000010000000000000000000
		   vec($_,13, 1) = 1   ==	8192 00000000000001000000000000000000
		   vec($_,14, 1) = 1   ==      16384 00000000000000100000000000000000
		   vec($_,15, 1) = 1   ==      32768 00000000000000010000000000000000
		   vec($_,16, 1) = 1   ==      65536 00000000000000001000000000000000
		   vec($_,17, 1) = 1   ==     131072 00000000000000000100000000000000
		   vec($_,18, 1) = 1   ==     262144 00000000000000000010000000000000
		   vec($_,19, 1) = 1   ==     524288 00000000000000000001000000000000
		   vec($_,20, 1) = 1   ==    1048576 00000000000000000000100000000000
		   vec($_,21, 1) = 1   ==    2097152 00000000000000000000010000000000
		   vec($_,22, 1) = 1   ==    4194304 00000000000000000000001000000000
		   vec($_,23, 1) = 1   ==    8388608 00000000000000000000000100000000
		   vec($_,24, 1) = 1   ==   16777216 00000000000000000000000010000000
		   vec($_,25, 1) = 1   ==   33554432 00000000000000000000000001000000
		   vec($_,26, 1) = 1   ==   67108864 00000000000000000000000000100000
		   vec($_,27, 1) = 1   ==  134217728 00000000000000000000000000010000
		   vec($_,28, 1) = 1   ==  268435456 00000000000000000000000000001000
		   vec($_,29, 1) = 1   ==  536870912 00000000000000000000000000000100
		   vec($_,30, 1) = 1   == 1073741824 00000000000000000000000000000010
		   vec($_,31, 1) = 1   == 2147483648 00000000000000000000000000000001
		   vec($_, 0, 2) = 1   ==	   1 10000000000000000000000000000000
		   vec($_, 1, 2) = 1   ==	   4 00100000000000000000000000000000
		   vec($_, 2, 2) = 1   ==	  16 00001000000000000000000000000000
		   vec($_, 3, 2) = 1   ==	  64 00000010000000000000000000000000
		   vec($_, 4, 2) = 1   ==	 256 00000000100000000000000000000000
		   vec($_, 5, 2) = 1   ==	1024 00000000001000000000000000000000
		   vec($_, 6, 2) = 1   ==	4096 00000000000010000000000000000000
		   vec($_, 7, 2) = 1   ==      16384 00000000000000100000000000000000
		   vec($_, 8, 2) = 1   ==      65536 00000000000000001000000000000000
		   vec($_, 9, 2) = 1   ==     262144 00000000000000000010000000000000
		   vec($_,10, 2) = 1   ==    1048576 00000000000000000000100000000000
		   vec($_,11, 2) = 1   ==    4194304 00000000000000000000001000000000
		   vec($_,12, 2) = 1   ==   16777216 00000000000000000000000010000000
		   vec($_,13, 2) = 1   ==   67108864 00000000000000000000000000100000
		   vec($_,14, 2) = 1   ==  268435456 00000000000000000000000000001000
		   vec($_,15, 2) = 1   == 1073741824 00000000000000000000000000000010
		   vec($_, 0, 2) = 2   ==	   2 01000000000000000000000000000000
		   vec($_, 1, 2) = 2   ==	   8 00010000000000000000000000000000
		   vec($_, 2, 2) = 2   ==	  32 00000100000000000000000000000000
		   vec($_, 3, 2) = 2   ==	 128 00000001000000000000000000000000
		   vec($_, 4, 2) = 2   ==	 512 00000000010000000000000000000000
		   vec($_, 5, 2) = 2   ==	2048 00000000000100000000000000000000
		   vec($_, 6, 2) = 2   ==	8192 00000000000001000000000000000000
		   vec($_, 7, 2) = 2   ==      32768 00000000000000010000000000000000
		   vec($_, 8, 2) = 2   ==     131072 00000000000000000100000000000000
		   vec($_, 9, 2) = 2   ==     524288 00000000000000000001000000000000
		   vec($_,10, 2) = 2   ==    2097152 00000000000000000000010000000000
		   vec($_,11, 2) = 2   ==    8388608 00000000000000000000000100000000
		   vec($_,12, 2) = 2   ==   33554432 00000000000000000000000001000000
		   vec($_,13, 2) = 2   ==  134217728 00000000000000000000000000010000
		   vec($_,14, 2) = 2   ==  536870912 00000000000000000000000000000100
		   vec($_,15, 2) = 2   == 2147483648 00000000000000000000000000000001
		   vec($_, 0, 4) = 1   ==	   1 10000000000000000000000000000000
		   vec($_, 1, 4) = 1   ==	  16 00001000000000000000000000000000
		   vec($_, 2, 4) = 1   ==	 256 00000000100000000000000000000000
		   vec($_, 3, 4) = 1   ==	4096 00000000000010000000000000000000
		   vec($_, 4, 4) = 1   ==      65536 00000000000000001000000000000000
		   vec($_, 5, 4) = 1   ==    1048576 00000000000000000000100000000000
		   vec($_, 6, 4) = 1   ==   16777216 00000000000000000000000010000000
		   vec($_, 7, 4) = 1   ==  268435456 00000000000000000000000000001000
		   vec($_, 0, 4) = 2   ==	   2 01000000000000000000000000000000
		   vec($_, 1, 4) = 2   ==	  32 00000100000000000000000000000000
		   vec($_, 2, 4) = 2   ==	 512 00000000010000000000000000000000
		   vec($_, 3, 4) = 2   ==	8192 00000000000001000000000000000000
		   vec($_, 4, 4) = 2   ==     131072 00000000000000000100000000000000
		   vec($_, 5, 4) = 2   ==    2097152 00000000000000000000010000000000
		   vec($_, 6, 4) = 2   ==   33554432 00000000000000000000000001000000
		   vec($_, 7, 4) = 2   ==  536870912 00000000000000000000000000000100
		   vec($_, 0, 4) = 4   ==	   4 00100000000000000000000000000000
		   vec($_, 1, 4) = 4   ==	  64 00000010000000000000000000000000
		   vec($_, 2, 4) = 4   ==	1024 00000000001000000000000000000000
		   vec($_, 3, 4) = 4   ==      16384 00000000000000100000000000000000
		   vec($_, 4, 4) = 4   ==     262144 00000000000000000010000000000000
		   vec($_, 5, 4) = 4   ==    4194304 00000000000000000000001000000000
		   vec($_, 6, 4) = 4   ==   67108864 00000000000000000000000000100000
		   vec($_, 7, 4) = 4   == 1073741824 00000000000000000000000000000010
		   vec($_, 0, 4) = 8   ==	   8 00010000000000000000000000000000
		   vec($_, 1, 4) = 8   ==	 128 00000001000000000000000000000000
		   vec($_, 2, 4) = 8   ==	2048 00000000000100000000000000000000
		   vec($_, 3, 4) = 8   ==      32768 00000000000000010000000000000000
		   vec($_, 4, 4) = 8   ==     524288 00000000000000000001000000000000
		   vec($_, 5, 4) = 8   ==    8388608 00000000000000000000000100000000
		   vec($_, 6, 4) = 8   ==  134217728 00000000000000000000000000010000
		   vec($_, 7, 4) = 8   == 2147483648 00000000000000000000000000000001
		   vec($_, 0, 8) = 1   ==	   1 10000000000000000000000000000000
		   vec($_, 1, 8) = 1   ==	 256 00000000100000000000000000000000
		   vec($_, 2, 8) = 1   ==      65536 00000000000000001000000000000000
		   vec($_, 3, 8) = 1   ==   16777216 00000000000000000000000010000000
		   vec($_, 0, 8) = 2   ==	   2 01000000000000000000000000000000
		   vec($_, 1, 8) = 2   ==	 512 00000000010000000000000000000000
		   vec($_, 2, 8) = 2   ==     131072 00000000000000000100000000000000
		   vec($_, 3, 8) = 2   ==   33554432 00000000000000000000000001000000
		   vec($_, 0, 8) = 4   ==	   4 00100000000000000000000000000000
		   vec($_, 1, 8) = 4   ==	1024 00000000001000000000000000000000
		   vec($_, 2, 8) = 4   ==     262144 00000000000000000010000000000000
		   vec($_, 3, 8) = 4   ==   67108864 00000000000000000000000000100000
		   vec($_, 0, 8) = 8   ==	   8 00010000000000000000000000000000
		   vec($_, 1, 8) = 8   ==	2048 00000000000100000000000000000000
		   vec($_, 2, 8) = 8   ==     524288 00000000000000000001000000000000
		   vec($_, 3, 8) = 8   ==  134217728 00000000000000000000000000010000
		   vec($_, 0, 8) = 16  ==	  16 00001000000000000000000000000000
		   vec($_, 1, 8) = 16  ==	4096 00000000000010000000000000000000
		   vec($_, 2, 8) = 16  ==    1048576 00000000000000000000100000000000
		   vec($_, 3, 8) = 16  ==  268435456 00000000000000000000000000001000
		   vec($_, 0, 8) = 32  ==	  32 00000100000000000000000000000000
		   vec($_, 1, 8) = 32  ==	8192 00000000000001000000000000000000
		   vec($_, 2, 8) = 32  ==    2097152 00000000000000000000010000000000
		   vec($_, 3, 8) = 32  ==  536870912 00000000000000000000000000000100
		   vec($_, 0, 8) = 64  ==	  64 00000010000000000000000000000000
		   vec($_, 1, 8) = 64  ==      16384 00000000000000100000000000000000
		   vec($_, 2, 8) = 64  ==    4194304 00000000000000000000001000000000
		   vec($_, 3, 8) = 64  == 1073741824 00000000000000000000000000000010
		   vec($_, 0, 8) = 128 ==	 128 00000001000000000000000000000000
		   vec($_, 1, 8) = 128 ==      32768 00000000000000010000000000000000
		   vec($_, 2, 8) = 128 ==    8388608 00000000000000000000000100000000
		   vec($_, 3, 8) = 128 == 2147483648 00000000000000000000000000000001

       wait    Behaves like the	wait(2)	system call on your system: it waits
	       for a child process to terminate	and returns the	pid of the de-
	       ceased process, or "-1" if there	are no child processes.	 The
	       status is returned in $?	 and "{^CHILD_ERROR_NATIVE}".  Note
	       that a return value of "-1" could mean that child processes are
	       being automatically reaped, as described	in perlipc.

       waitpid PID,FLAGS
	       Waits for a particular child process to terminate and returns
	       the pid of the deceased process,	or "-1"	if there is no such
	       child process.  On some systems,	a value	of 0 indicates that
	       there are processes still running.  The status is returned in
	       $? and "{^CHILD_ERROR_NATIVE}".	If you say

		   use POSIX ":sys_wait_h";
		   #...
		   do {
		       $kid = waitpid(-1, WNOHANG);
		   } while $kid	> 0;

	       then you	can do a non-blocking wait for all pending zombie pro-
	       cesses.	Non-blocking wait is available on machines supporting
	       either the waitpid(2) or	wait4(2) system	calls.	However, wait-
	       ing for a particular pid	with FLAGS of 0	is implemented every-
	       where.  (Perl emulates the system call by remembering the sta-
	       tus values of processes that have exited	but have not been har-
	       vested by the Perl script yet.)

	       Note that on some systems, a return value of "-1" could mean
	       that child processes are	being automatically reaped.  See per-
	       lipc for	details, and for other examples.

       wantarray
	       Returns true if the context of the currently executing subrou-
	       tine or "eval" is looking for a list value.  Returns false if
	       the context is looking for a scalar.  Returns the undefined
	       value if	the context is looking for no value (void context).

		   return unless defined wantarray;    # don't bother doing more
		   my @a = complex_calculation();
		   return wantarray ? @a : "@a";

	       "wantarray()"'s result is unspecified in	the top	level of a
	       file, in	a "BEGIN", "CHECK", "INIT" or "END" block, or in a
	       "DESTROY" method.

	       This function should have been named wantlist() instead.

       warn LIST
	       Prints the value	of LIST	to STDERR.  If the last	element	of
	       LIST does not end in a newline, it appends the same file/line
	       number text as "die" does.

	       If LIST is empty	and $@ already contains	a value	(typically
	       from a previous eval) that value	is used	after appending
	       "\t...caught" to	$@.  This is useful for	staying	almost,	but
	       not entirely similar to "die".

	       If $@ is	empty then the string "Warning:	Something's wrong" is
	       used.

	       No message is printed if	there is a $SIG{__WARN__} handler in-
	       stalled.	 It is the handler's responsibility to deal with the
	       message as it sees fit (like, for instance, converting it into
	       a "die").  Most handlers	must therefore make arrangements to
	       actually	display	the warnings that they are not prepared	to
	       deal with, by calling "warn" again in the handler.  Note	that
	       this is quite safe and will not produce an endless loop,	since
	       "__WARN__" hooks	are not	called from inside one.

	       You will	find this behavior is slightly different from that of
	       $SIG{__DIE__} handlers (which don't suppress the	error text,
	       but can instead call "die" again	to change it).

	       Using a "__WARN__" handler provides a powerful way to silence
	       all warnings (even the so-called	mandatory ones).  An example:

		   # wipe out *all* compile-time warnings
		   BEGIN { $SIG{'__WARN__'} = sub { warn $_[0] if $DOWARN } }
		   my $foo = 10;
		   my $foo = 20;	  # no warning about duplicate my $foo,
					  # but	hey, you asked for it!
		   # no	compile-time or	run-time warnings before here
		   $DOWARN = 1;

		   # run-time warnings enabled after here
		   warn	"\$foo is alive	and $foo!";	# does show up

	       See perlvar for details on setting %SIG entries,	and for	more
	       examples.  See the Carp module for other	kinds of warnings us-
	       ing its carp() and cluck() functions.

       write FILEHANDLE
       write EXPR
       write   Writes a	formatted record (possibly multi-line) to the speci-
	       fied FILEHANDLE,	using the format associated with that file.
	       By default the format for a file	is the one having the same
	       name as the filehandle, but the format for the current output
	       channel (see the	"select" function) may be set explicitly by
	       assigning the name of the format	to the $~ variable.

	       Top of form processing is handled automatically:	 if there is
	       insufficient room on the	current	page for the formatted record,
	       the page	is advanced by writing a form feed, a special top-of-
	       page format is used to format the new page header, and then the
	       record is written.  By default the top-of-page format is	the
	       name of the filehandle with "_TOP" appended, but	it may be dy-
	       namically set to	the format of your choice by assigning the
	       name to the $^ variable while the filehandle is selected.  The
	       number of lines remaining on the	current	page is	in variable
	       "$-", which can be set to 0 to force a new page.

	       If FILEHANDLE is	unspecified, output goes to the	current	de-
	       fault output channel, which starts out as STDOUT	but may	be
	       changed by the "select" operator.  If the FILEHANDLE is an
	       EXPR, then the expression is evaluated and the resulting	string
	       is used to look up the name of the FILEHANDLE at	run time.  For
	       more on formats,	see perlform.

	       Note that write is not the opposite of "read".  Unfortunately.

       y///    The transliteration operator.  Same as "tr///".	See perlop.

perl v5.8.9			  2007-11-17			   PERLFUNC(1)

NAME | DESCRIPTION

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=perlfunc&manpath=FreeBSD+7.2-RELEASE+and+Ports>

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