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PERLREREF(1)	       Perl Programmers	Reference Guide		  PERLREREF(1)

NAME
       perlreref - Perl	Regular	Expressions Reference

DESCRIPTION
       This is a quick reference to Perl's regular expressions.	 For full
       information see perlre and perlop, as well as the "SEE ALSO" section in
       this document.

   OPERATORS
       "=~" determines to which	variable the regex is applied.	In its
       absence,	$_ is used.

	   $var	=~ /foo/;

       "!~" determines to which	variable the regex is applied, and negates the
       result of the match; it returns false if	the match succeeds, and	true
       if it fails.

	   $var	!~ /foo/;

       "m/pattern/msixpogcdualn" searches a string for a pattern match,
       applying	the given options.

	   m  Multiline	mode - ^ and $ match internal lines
	   s  match as a Single	line - . matches \n
	   i  case-Insensitive
	   x  eXtended legibility - free whitespace and	comments
	   p  Preserve a copy of the matched string -
	      ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH} will be defined.
	   o  compile pattern Once
	   g  Global - all occurrences
	   c  don't reset pos on failed	matches	when using /g
	   a  restrict \d, \s, \w and [:posix:]	to match ASCII only
	   aa (two a's)	also /i	matches	exclude	ASCII/non-ASCII
	   l  match according to current locale
	   u  match according to Unicode rules
	   d  match according to native	rules unless something indicates
	      Unicode
	   n  Non-capture mode.	Don't let () fill in $1, $2, etc...

       If 'pattern' is an empty	string,	the last successfully matched regex is
       used. Delimiters	other than '/' may be used for both this operator and
       the following ones. The leading "m" can be omitted if the delimiter is
       '/'.

       "qr/pattern/msixpodualn"	lets you store a regex in a variable, or pass
       one around. Modifiers as	for "m//", and are stored within the regex.

       "s/pattern/replacement/msixpogcedual" substitutes matches of 'pattern'
       with 'replacement'. Modifiers as	for "m//", with	two additions:

	   e  Evaluate 'replacement' as	an expression
	   r  Return substitution and leave the	original string	untouched.

       'e' may be specified multiple times. 'replacement' is interpreted as a
       double quoted string unless a single-quote ("'")	is the delimiter.

       "m?pattern?" is like "m/pattern/" but matches only once.	No alternate
       delimiters can be used.	Must be	reset with reset().

   SYNTAX
	\	Escapes	the character immediately following it
	.	Matches	any single character except a newline (unless /s is
		  used)
	^	Matches	at the beginning of the	string (or line, if /m is used)
	$	Matches	at the end of the string (or line, if /m is used)
	*	Matches	the preceding element 0	or more	times
	+	Matches	the preceding element 1	or more	times
	?	Matches	the preceding element 0	or 1 times
	{...}	Specifies a range of occurrences for the element preceding it
	[...]	Matches	any one	of the characters contained within the brackets
	(...)	Groups subexpressions for capturing to $1, $2...
	(?:...)	Groups subexpressions without capturing	(cluster)
	|	Matches	either the subexpression preceding or following	it
	\g1 or \g{1}, \g2 ...	 Matches the text from the Nth group
	\1, \2,	\3 ...		 Matches the text from the Nth group
	\g-1 or	\g{-1},	\g-2 ... Matches the text from the Nth previous	group
	\g{name}     Named backreference
	\k<name>     Named backreference
	\k'name'     Named backreference
	(?P=name)    Named backreference (python syntax)

   ESCAPE SEQUENCES
       These work as in	normal strings.

	  \a	   Alarm (beep)
	  \e	   Escape
	  \f	   Formfeed
	  \n	   Newline
	  \r	   Carriage return
	  \t	   Tab
	  \037	   Char	whose ordinal is the 3 octal digits, max \777
	  \o{2307} Char	whose ordinal is the octal number, unrestricted
	  \x7f	   Char	whose ordinal is the 2 hex digits, max \xFF
	  \x{263a} Char	whose ordinal is the hex number, unrestricted
	  \cx	   Control-x
	  \N{name} A named Unicode character or	character sequence
	  \N{U+263D} A Unicode character by hex	ordinal

	  \l  Lowercase	next character
	  \u  Titlecase	next character
	  \L  Lowercase	until \E
	  \U  Uppercase	until \E
	  \F  Foldcase until \E
	  \Q  Disable pattern metacharacters until \E
	  \E  End modification

       For Titlecase, see "Titlecase".

       This one	works differently from normal strings:

	  \b  An assertion, not	backspace, except in a character class

   CHARACTER CLASSES
	  [amy]	   Match 'a', 'm' or 'y'
	  [f-j]	   Dash	specifies "range"
	  [f-j-]   Dash	escaped	or at start or end means 'dash'
	  [^f-j]   Caret indicates "match any character	_except_ these"

       The following sequences (except "\N") work within or without a
       character class.	 The first six are locale aware, all are Unicode
       aware. See perllocale and perlunicode for details.

	  \d	  A digit
	  \D	  A nondigit
	  \w	  A word character
	  \W	  A non-word character
	  \s	  A whitespace character
	  \S	  A non-whitespace character
	  \h	  A horizontal whitespace
	  \H	  A non	horizontal whitespace
	  \N	  A non	newline	(when not followed by '{NAME}';;
		  not valid in a character class; equivalent to	[^\n]; it's
		  like '.' without /s modifier)
	  \v	  A vertical whitespace
	  \V	  A non	vertical whitespace
	  \R	  A generic newline	      (?>\v|\x0D\x0A)

	  \pP	  Match	P-named	(Unicode) property
	  \p{...} Match	Unicode	property with name longer than 1 character
	  \PP	  Match	non-P
	  \P{...} Match	lack of	Unicode	property with name longer than 1 char
	  \X	  Match	Unicode	extended grapheme cluster

       POSIX character classes and their Unicode and Perl equivalents:

		   ASCII-	  Full-
	  POSIX	   range	  range	   backslash
	[[:...:]]  \p{...}	  \p{...}   sequence	Description

	-----------------------------------------------------------------------
	alnum	PosixAlnum	 XPosixAlnum		'alpha'	plus 'digit'
	alpha	PosixAlpha	 XPosixAlpha		Alphabetic characters
	ascii	ASCII					Any ASCII character
	blank	PosixBlank	 XPosixBlank   \h	Horizontal whitespace;
							  full-range also
							  written as
							  \p{HorizSpace} (GNU
							  extension)
	cntrl	PosixCntrl	 XPosixCntrl		Control	characters
	digit	PosixDigit	 XPosixDigit   \d	Decimal	digits
	graph	PosixGraph	 XPosixGraph		'alnum'	plus 'punct'
	lower	PosixLower	 XPosixLower		Lowercase characters
	print	PosixPrint	 XPosixPrint		'graph'	plus 'space',
							  but not any Controls
	punct	PosixPunct	 XPosixPunct		Punctuation and	Symbols
							  in ASCII-range; just
							  punct	outside	it
	space	PosixSpace	 XPosixSpace   \s	Whitespace
	upper	PosixUpper	 XPosixUpper		Uppercase characters
	word	PosixWord	 XPosixWord    \w	'alnum'	+ Unicode marks
							   + connectors, like
							   '_' (Perl extension)
	xdigit	ASCII_Hex_Digit	 XPosixDigit		Hexadecimal digit,
							   ASCII-range is
							   [0-9A-Fa-f]

       Also, various synonyms like "\p{Alpha}" for "\p{XPosixAlpha}"; all
       listed in "Properties accessible	through	\p{} and \P{}" in perluniprops

       Within a	character class:

	   POSIX      traditional   Unicode
	 [:digit:]	 \d	   \p{Digit}
	 [:^digit:]	 \D	   \P{Digit}

   ANCHORS
       All are zero-width assertions.

	  ^  Match string start	(or line, if /m	is used)
	  $  Match string end (or line,	if /m is used) or before newline
	  \b{} Match boundary of type specified	within the braces
	  \B{} Match wherever \b{} doesn't match
	  \b Match word	boundary (between \w and \W)
	  \B Match except at word boundary (between \w and \w or \W and	\W)
	  \A Match string start	(regardless of /m)
	  \Z Match string end (before optional newline)
	  \z Match absolute string end
	  \G Match where previous m//g left off
	  \K Keep the stuff left of the	\K, don't include it in	$&

   QUANTIFIERS
       Quantifiers are greedy by default and match the longest leftmost.

	  Maximal Minimal Possessive Allowed range
	  ------- ------- ---------- -------------
	  {n,m}	  {n,m}?  {n,m}+     Must occur	at least n times
				     but no more than m	times
	  {n,}	  {n,}?	  {n,}+	     Must occur	at least n times
	  {,n}	  {,n}?	  {,n}+	     Must occur	at most	n times
	  {n}	  {n}?	  {n}+	     Must occur	exactly	n times
	  *	  *?	  *+	     0 or more times (same as {0,})
	  +	  +?	  ++	     1 or more times (same as {1,})
	  ?	  ??	  ?+	     0 or 1 time (same as {0,1})

       The possessive forms (new in Perl 5.10) prevent backtracking: what gets
       matched by a pattern with a possessive quantifier will not be
       backtracked into, even if that causes the whole match to	fail.

   EXTENDED CONSTRUCTS
	  (?#text)	    A comment
	  (?:...)	    Groups subexpressions without capturing (cluster)
	  (?pimsx-imsx:...) Enable/disable option (as per m// modifiers)
	  (?=...)	    Zero-width positive	lookahead assertion
	  (*pla:...)	    Same, starting in 5.32; experimentally in 5.28
	  (*positive_lookahead:...) Same, same versions	as *pla
	  (?!...)	    Zero-width negative	lookahead assertion
	  (*nla:...)	    Same, starting in 5.32; experimentally in 5.28
	  (*negative_lookahead:...) Same, same versions	as *nla
	  (?<=...)	    Zero-width positive	lookbehind assertion
	  (*plb:...)	    Same, starting in 5.32; experimentally in 5.28
	  (*positive_lookbehind:...) Same, same	versions as *plb
	  (?<!...)	    Zero-width negative	lookbehind assertion
	  (*nlb:...)	    Same, starting in 5.32; experimentally in 5.28
	  (*negative_lookbehind:...) Same, same	versions as *plb
	  (?>...)	    Grab what we can, prohibit backtracking
	  (*atomic:...)	    Same, starting in 5.32; experimentally in 5.28
	  (?|...)	    Branch reset
	  (?<name>...)	    Named capture
	  (?'name'...)	    Named capture
	  (?P<name>...)	    Named capture (python syntax)
	  (?[...])	    Extended bracketed character class
	  (?{ code })	    Embedded code, return value	becomes	$^R
	  (??{ code })	    Dynamic regex, return value	used as	regex
	  (?N)		    Recurse into subpattern number N
	  (?-N), (?+N)	    Recurse into Nth previous/next subpattern
	  (?R),	(?0)	    Recurse at the beginning of	the whole pattern
	  (?&name)	    Recurse into a named subpattern
	  (?P>name)	    Recurse into a named subpattern (python syntax)
	  (?(cond)yes|no)
	  (?(cond)yes)	    Conditional	expression, where "(cond)" can be:
			    (?=pat)   lookahead; also (*pla:pat)
				      (*positive_lookahead:pat)
			    (?!pat)   negative lookahead; also (*nla:pat)
				      (*negative_lookahead:pat)
			    (?<=pat)  lookbehind; also (*plb:pat)
				      (*lookbehind:pat)
			    (?<!pat)  negative lookbehind; also	(*nlb:pat)
				      (*negative_lookbehind:pat)
			    (N)	      subpattern N has matched something
			    (<name>)  named subpattern has matched something
			    ('name')  named subpattern has matched something
			    (?{code}) code condition
			    (R)	      true if recursing
			    (RN)      true if recursing	into Nth subpattern
			    (R&name)  true if recursing	into named subpattern
			    (DEFINE)  always false, no no-pattern allowed

   VARIABLES
	  $_	Default	variable for operators to use

	  $`	Everything prior to matched string
	  $&	Entire matched string
	  $'	Everything after to matched string

	  ${^PREMATCH}	 Everything prior to matched string
	  ${^MATCH}	 Entire	matched	string
	  ${^POSTMATCH}	 Everything after to matched string

       Note to those still using Perl 5.18 or earlier: The use of "$`",	$& or
       "$'" will slow down all regex use within	your program. Consult perlvar
       for "@-"	to see equivalent expressions that won't cause slow down.  See
       also Devel::SawAmpersand. Starting with Perl 5.10, you can also use the
       equivalent variables "${^PREMATCH}", "${^MATCH}"	and "${^POSTMATCH}",
       but for them to be defined, you have to specify the "/p"	(preserve)
       modifier	on your	regular	expression.  In	Perl 5.20, the use of "$`", $&
       and "$'"	makes no speed difference.

	  $1, $2 ...  hold the Xth captured expr
	  $+	Last parenthesized pattern match
	  $^N	Holds the most recently	closed capture
	  $^R	Holds the result of the	last (?{...}) expr
	  @-	Offsets	of starts of groups. $-[0] holds start of whole	match
	  @+	Offsets	of ends	of groups. $+[0] holds end of whole match
	  %+	Named capture groups
	  %-	Named capture groups, as array refs

       Captured	groups are numbered according to their opening paren.

   FUNCTIONS
	  lc	      Lowercase	a string
	  lcfirst     Lowercase	first char of a	string
	  uc	      Uppercase	a string
	  ucfirst     Titlecase	first char of a	string
	  fc	      Foldcase a string

	  pos	      Return or	set current match position
	  quotemeta   Quote metacharacters
	  reset	      Reset m?pattern? status
	  study	      Analyze string for optimizing matching

	  split	      Use a regex to split a string into parts

       The first five of these are like	the escape sequences "\L", "\l", "\U",
       "\u", and "\F".	For Titlecase, see "Titlecase";	For Foldcase, see
       "Foldcase".

   TERMINOLOGY
       Titlecase

       Unicode concept which most often	is equal to uppercase, but for certain
       characters like the German "sharp s" there is a difference.

       Foldcase

       Unicode form that is useful when	comparing strings regardless of	case,
       as certain characters have complex one-to-many case mappings. Primarily
       a variant of lowercase.

AUTHOR
       Iain Truskett. Updated by the Perl 5 Porters.

       This document may be distributed	under the same terms as	Perl itself.

SEE ALSO
       o   perlretut for a tutorial on regular expressions.

       o   perlrequick for a rapid tutorial.

       o   perlre for more details.

       o   perlvar for details on the variables.

       o   perlop for details on the operators.

       o   perlfunc for	details	on the functions.

       o   perlfaq6 for	FAQs on	regular	expressions.

       o   perlrebackslash for a reference on backslash	sequences.

       o   perlrecharclass for a reference on character	classes.

       o   The re module to alter behaviour and	aid debugging.

       o   "Debugging Regular Expressions" in perldebug

       o   perluniintro, perlunicode, charnames	and perllocale for details on
	   regexes and internationalisation.

       o   Mastering Regular Expressions by Jeffrey Friedl
	   (<http://oreilly.com/catalog/9780596528126/>) for a thorough
	   grounding and reference on the topic.

THANKS
       David P.C. Wollmann, Richard Soderberg, Sean M. Burke, Tom
       Christiansen, Jim Cromie, and Jeffrey Goff for useful advice.

perl v5.35.11			  2022-03-27			  PERLREREF(1)

NAME | DESCRIPTION | AUTHOR | SEE ALSO | THANKS

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