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PadWalker(3)	      User Contributed Perl Documentation	  PadWalker(3)

NAME
       PadWalker - play	with other peoples' lexical variables

SYNOPSIS
	 use PadWalker qw(peek_my peek_our peek_sub closed_over);
	 ...

DESCRIPTION
       PadWalker is a module which allows you to inspect (and even change!)
       lexical variables in any	subroutine which called	you. It	will only show
       those variables which are in scope at the point of the call.

       PadWalker is particularly useful	for debugging. It's even used by
       Perl's built-in debugger. (It can also be used for evil,	of course.)

       I wouldn't recommend using PadWalker directly in	production code, but
       it's your call. Some of the modules that	use PadWalker internally are
       certainly safe for and useful in	production.

       peek_my LEVEL
       peek_our	LEVEL
	   The LEVEL argument is interpreted just like the argument to
	   "caller".  So peek_my(0) returns a reference	to a hash of all the
	   "my"	variables that are currently in	scope; peek_my(1) returns a
	   reference to	a hash of all the "my" variables that are in scope at
	   the point where the current sub was called, and so on.

	   "peek_our" works in the same	way, except that it lists the "our"
	   variables rather than the "my" variables.

	   The hash associates each variable name with a reference to its
	   value. The variable names include the sigil,	so the variable	$x is
	   represented by the string '$x'.

	   For example:

	     my	$x = 12;
	     my	$h = peek_my (0);
	     ${$h->{'$x'}}++;

	     print $x;	# prints 13

	   Or a	more complex example:

	     sub increment_my_x	{
	       my $h = peek_my (1);
	       ${$h->{'$x'}}++;
	     }

	     my	$x=5;
	     increment_my_x;
	     print $x;	# prints 6

       peek_sub	SUB
	   The "peek_sub" routine takes	a coderef as its argument, and returns
	   a hash of the "my" variables	used in	that sub. The values will
	   usually be undefined	unless the sub is in use (i.e. in the call-
	   chain) at the time. On the other hand:

	     my	$x = "Hello!";
	     my	$r = peek_sub(sub {$x})->{'$x'};
	     print "$$r\n";	   # prints 'Hello!'

	   If the sub defines several "my" variables with the same name,
	   you'll get the last one. I don't know of any	use for	"peek_sub"
	   that	isn't broken as	a result of this, and it will probably be
	   deprecated in a future version in favour of some alternative
	   interface.

       closed_over SUB
	   "closed_over" is similar to "peek_sub", except that it only lists
	   the "my" variables which are	used in	the subroutine but defined
	   outside: in other words, the	variables which	it closes over.	This
	   does	have reasonable	uses: see Data::Dump::Streamer,	for example (a
	   future version of which may in fact use "closed_over").

       set_closed_over SUB, HASH_REF
	   "set_closed_over" reassigns the pad variables that are closed over
	   by the subroutine.

	   The second argument is a hash of references,	much like the one
	   returned from "closed_over".

       var_name	LEVEL, VAR_REF
       var_name	SUB,   VAR_REF
	   "var_name(sub, var_ref)" returns the	name of	the variable referred
	   to by "var_ref", provided it	is a "my" variable used	in the sub.
	   The "sub" parameter can be either a CODE reference or a number. If
	   it's	a number, it's treated the same	way as the argument to
	   "peek_my".

	   For example,

	     my	$foo;
	     print var_name(0, \$foo);	  # prints '$foo'

	     sub my_name {
	       return var_name(1, shift);
	     }
	     print my_name(\$foo);	  # ditto

AUTHOR
       Robin Houston <robin@cpan.org>

       With contributions from Richard Soberberg, Jesse	Luehrs and Yuval
       Kogman, bug-spotting from Peter Scott, Dave Mitchell and	Goro Fuji, and
       suggestions from	demerphq.

SEE ALSO
       Devel::LexAlias,	Devel::Caller, Sub::Parameters

COPYRIGHT
       Copyright (c) 2000-2009,	Robin Houston. All Rights Reserved.  This
       module is free software.	It may be used,	redistributed and/or modified
       under the same terms as Perl itself.

perl v5.32.1			  2020-09-27			  PadWalker(3)

NAME | SYNOPSIS | DESCRIPTION | AUTHOR | SEE ALSO | COPYRIGHT

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