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

       perlreref - Perl Regular Expressions Reference

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


	 =~ 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/igmsoxc searches a string for a pattern match,
	    applying the given options.

	       i  case-Insensitive
	       g  Global - all occurrences
	       m  Multiline mode - ^ and $ match internal lines
	       s  match as a Single line - . matches \n
	       o  compile pattern Once
	       x  eXtended legibility - free whitespace and comments
	       c  dont reset pos on failed matches when using /g

	    If pattern is an empty string, the last I matched
	    regex is used. Delimiters other than / may be used for both this
	    operator and the following ones.

	 qr/pattern/imsox 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/igmsoxe substitutes matches of
	    pattern with replacement. Modifiers as for m//
	    with one addition:

	       e  Evaluate replacement as an expression

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

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


	  \	  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
	  \1, \2 ...  The text from the Nth group


       These work as in normal strings.

	  \a	   Alarm (beep)
	  \e	   Escape
	  \f	   Formfeed
	  \n	   Newline
	  \r	   Carriage return
	  \t	   Tab
	  \037	   Any octal ASCII value
	  \x7f	   Any hexadecimal ASCII value
	  \x{263a} A wide hexadecimal value
	  \cx	   Control-x
	  \N{name} A named character

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

       For Titlecase, see "Titlecase".

       This one works differently from normal strings:

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


	  [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 work within or without a character class.  The
       first six are locale aware, all are Unicode aware.  The default charac
       ter class equivalent are given.	See perllocale and perlunicode for

	  \d	  A digit		      [0-9]
	  \D	  A nondigit		      [^0-9]
	  \w	  A word character	      [a-zA-Z0-9_]
	  \W	  A non-word character	      [^a-zA-Z0-9_]
	  \s	  A whitespace character      [ \t\n\r\f]
	  \S	  A non-whitespace character  [^ \t\n\r\f]

	  \C	  Match a byte (with Unicode, . matches a character)
	  \pP	  Match P-named (Unicode) property
	  \p{...} Match Unicode property with long name
	  \PP	  Match non-P
	  \P{...} Match lack of Unicode property with long name
	  \X	  Match extended unicode sequence

       POSIX character classes and their Unicode and Perl equivalents:

	  alnum   IsAlnum	       Alphanumeric
	  alpha   IsAlpha	       Alphabetic
	  ascii   IsASCII	       Any ASCII char
	  blank   IsSpace  [ \t]       Horizontal whitespace (GNU extension)
	  cntrl   IsCntrl	       Control characters
	  digit   IsDigit  \d	       Digits
	  graph   IsGraph	       Alphanumeric and punctuation
	  lower   IsLower	       Lowercase chars (locale and Unicode aware)
	  print   IsPrint	       Alphanumeric, punct, and space
	  punct   IsPunct	       Punctuation
	  space   IsSpace  [\s\ck]     Whitespace
		  IsSpacePerl	\s     Perls whitespace definition
	  upper   IsUpper	       Uppercase chars (locale and Unicode aware)
	  word	  IsWord   \w	       Alphanumeric plus _ (Perl extension)
	  xdigit  IsXDigit [0-9A-Fa-f] Hexadecimal digit

       Within a character class:

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


       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 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


       Quantifiers are greedy by default -- match the longest leftmost.

	  Maximal Minimal Allowed range
	  ------- ------- -------------
	  {n,m}   {n,m}?  Must occur at least n times but no more than m times
	  {n,}	  {n,}?   Must occur at least n times
	  {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})

       There is no quantifier {,n} -- that gets understood as a literal


	  (?#text)	   A comment
	  (?imxs-imsx:...) Enable/disable option (as per m// modifiers)
	  (?=...)	   Zero-width positive lookahead assertion
	  (?!...)	   Zero-width negative lookahead assertion
	  (?<=...)	   Zero-width positive lookbehind assertion
	  (?...)	   Grab what we can, prohibit backtracking
	  (?{ code })	   Embedded code, return value becomes $^R
	  (??{ code })	   Dynamic regex, return value used as regex
	  (?(cond)yes|no)  cond being integer corresponding to capturing parens
	  (?(cond)yes)	      or a lookaround/eval zero-width assertion


	  $_	Default variable for operators to use
	  $*	Enable multiline matching (deprecated; not in 5.9.0 or later)

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

       The use of those last three will slow down all regex use within your
       program. Consult perlvar for @LAST_MATCH_START to see equivalent
       expressions that wont cause slow down.  See also Devel::SawAmpersand.

	  $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

       Captured groups are numbered according to their opening paren.


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

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

	  split       Use regex to split a string into parts

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



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

       Iain Truskett.

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

	  perlretut for a tutorial on regular expressions.

	  perlrequick for a rapid tutorial.

	  perlre for more details.

	  perlvar for details on the variables.

	  perlop for details on the operators.

	  perlfunc for details on the functions.

	  perlfaq6 for FAQs on regular expressions.

	  The re module to alter behaviour and aid debugging.

	  "Debugging regular expressions" in perldebug

	  perluniintro, perlunicode, charnames and locale for details on
	   regexes and internationalisation.

	  Mastering Regular Expressions by Jeffrey Friedl
	   (http://regex.info/) for a thorough grounding and reference on the

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

perl v5.8.8			  2008-04-25			  PERLREREF(1)

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