This is a quick reference to Perl's regular expressions.
For full information see L<perlre> and L<perlop>, as well
-as the L<references|/"SEE ALSO"> section in this document.
+as the L</"SEE ALSO"> section in this document.
-=head1 OPERATORS
+=head2 OPERATORS
=~ determines to which variable the regex is applied.
- In its absence, C<$_> is used.
+ 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.
s match as a Single line - . matches \n
o compile pattern Once
x eXtended legibility - free whitespace and comments
- c don't reset pos on fails when using /g
+ c don't reset pos on failed matches when using /g
- If C<pattern> is an empty string, the last I<successfully> match
- regex is used. Delimiters other than C</> may be used for both this
+ If 'pattern' is an empty string, the last I<successfully> 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 C<m//> and are stored
+ or pass one around. Modifiers as for m// and are stored
within the regex.
s/pattern/replacement/igmsoxe substitutes matches of
- C<pattern> with C<replacement>. Modifiers as for C<m//>
- with addition of C<e>:
+ '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 C<m/pattern/> but matches only once. No alternate
- delimiters can be used. Must be reset with 'reset'.
-
-=head1 SYNTAX
-
- \ Escapes the character(s) 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 regular expressions
- | Matches either the expression preceding or following it
+ ?pattern? is like m/pattern/ but matches only once. No alternate
+ delimiters can be used. Must be reset with L<reset|perlfunc/reset>.
+
+=head2 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
\1, \2 ... The text from the Nth group
=head2 ESCAPE SEQUENCES
\n Newline
\r Carriage return
\t Tab
- \038 Any octal ASCII value
+ \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 until next character
- \u Uppercase until next 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 L</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 char any _except_ these"
+ [^f-j] Caret indicates "match any character _except_ these"
-The following work within or without a character class:
+The following sequences work within or without a character class.
+The first six are locale aware, all are Unicode aware. The default
+character class equivalent are given. See L<perllocale> and
+L<perlunicode> for details.
- \d A digit, same as [0-9]
- \D A nondigit, same as [^0-9]
- \w A word character (alphanumeric), same as [a-zA-Z_0-9]
- \W A non-word character, [^a-zA-Z_0-9]
- \s A whitespace character, same as [ \t\n\r\f]
- \S A non-whitespace character, [^ \t\n\r\f]
- \C Match a byte (with Unicode. '.' matches char)
+ \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
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)
- cntrl IsCntrl Control characters
- digit IsDigit \d Digits
- graph IsGraph Alphanumeric and punctuation
- lower IsLower Lowercase chars (locale aware)
- print IsPrint Alphanumeric, punct, and space
- punct IsPunct Punctuation
- space IsSpace [\s\ck] Whitespace
- IsSpacePerl \s Perl's whitespace definition
- upper IsUpper Uppercase chars (locale aware)
- word IsWord \w Alphanumeric plus _ (Perl)
- xdigit IsXDigit [\dA-Fa-f] Hexadecimal digit
+ 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 Perl's 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:
^ 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
+ \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 (preceding optional newline)
+ \Z Match string end (before optional newline)
\z Match absolute string end
\G Match where previous m//g left off
- \c Suppresses resetting of search position when used with /g.
- Without \c, search pattern is reset to the beginning of the string
=head2 QUANTIFIERS
-Quantifiers are greedy by default --- match the B<longest> leftmost.
+Quantifiers are greedy by default -- match the B<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 match exactly 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 string.
+
=head2 EXTENDED CONSTRUCTS
(?#text) A comment
- (?:...) Cluster without capturing
- (?imxs-imsx:...) Enable/disable option (as per m//)
+ (?imxs-imsx:...) Enable/disable option (as per m// modifiers)
(?=...) Zero-width positive lookahead assertion
(?!...) Zero-width negative lookahead assertion
- (?<...) Zero-width positive lookbehind assertion
+ (?<=...) Zero-width positive lookbehind assertion
(?<!...) Zero-width negative 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 int corresponding to capturing parens
+ (?(cond)yes|no) cond being integer corresponding to capturing parens
(?(cond)yes) or a lookaround/eval zero-width assertion
-=head1 VARIABLES
+=head2 VARIABLES
$_ Default variable for operators to use
- $* Enable multiline matching (deprecated; not in 5.8.1+)
+ $* Enable multiline matching (deprecated; not in 5.9.0 or later)
$& Entire matched string
$` Everything prior to matched string
$+ 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
+ @- Offsets of starts of groups. $-[0] holds start of whole match
+ @+ Offsets of ends of groups. $+[0] holds end of whole match
-Capture groups are numbered according to their I<opening> paren.
+Captured groups are numbered according to their I<opening> paren.
-=head1 FUNCTIONS
+=head2 FUNCTIONS
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
split Use regex to split a string into parts
+The first four of these are like the escape sequences C<\L>, C<\l>,
+C<\U>, and C<\u>. For Titlecase, see L</Titlecase>.
+
+=head2 TERMINOLOGY
+
+=head3 Titlecase
+
+Unicode concept which most often is equal to uppercase, but for
+certain characters like the German "sharp s" there is a difference.
+
=head1 AUTHOR
Iain Truskett.
Richard Soderberg,
Sean M. Burke,
Tom Christiansen,
+Jim Cromie,
and
Jeffrey Goff
for useful advice.
+
+=cut
https://perl5.git.perl.org / perl5.git / blobdiff