Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
gm

Test String

Code Generator

Language

Generated Code

use strict; my $str = 'Valid Semantic Versions ## [Unreleased] ## Unreleased ## foo ## [foo] ## [0.0.4] ## [1.2.3] ## [10.20.30] ## [1.1.2-prerelease+meta] ## [1.1.2+meta] ## [1.1.2+meta-valid] ## [1.0.0-alpha] ## [1.0.0-beta] ## [1.0.0-alpha.beta] ## [1.0.0-alpha.beta.1] ## [1.0.0-alpha.1] ## [1.0.0-alpha0.valid] ## [1.0.0-alpha.0valid] ## [1.0.0-alpha-a.b-c-somethinglong+build.1-aef.1-its-okay] ## [1.0.0-rc.1+build.1] ## [2.0.0-rc.1+build.123] ## [1.2.3-beta] ## [10.2.3-DEV-SNAPSHOT] ## [1.2.3-SNAPSHOT-123] ## [1.0.0] ## [2.0.0] ## [1.1.7] ## [2.0.0+build.1848] ## [2.0.1-alpha.1227] ## [1.0.0-alpha+beta] ## [1.2.3----RC-SNAPSHOT.12.9.1--.12+788] ## [1.2.3----R-S.12.9.1--.12+meta] ## [1.2.3----RC-SNAPSHOT.12.9.1--.12] ## [1.0.0+0.build.1-rc.10000aaa-kk-0.1] ## [99999999999999999999999.999999999999999999.99999999999999999] ## [1.0.0-0A.is.legal] Invalid Semantic Versions ## [1] ## [1.2] ## [1.2.3-0123] ## [1.2.3-0123.0123] ## [1.1.2+.123] ## [+invalid] ## [-invalid] ## [-invalid+invalid] ## [-invalid.01] ## [alpha] ## [alpha.beta] ## [alpha.beta.1] ## [alpha.1] ## [alpha+beta] ## [alpha_beta] ## [alpha.] ## [alpha..] ## [beta] ## [1.0.0-alpha_beta] ## [-alpha.] ## [1.0.0-alpha..] ## [1.0.0-alpha..1] ## [1.0.0-alpha...1] ## [1.0.0-alpha....1] ## [1.0.0-alpha.....1] ## [1.0.0-alpha......1] ## [1.0.0-alpha.......1] ## [01.1.1] ## [1.01.1] ## [1.1.01] ## [1.2] ## [1.2.3.DEV] ## [1.2-SNAPSHOT] ## [1.2.31.2.3----RC-SNAPSHOT.12.09.1--..12+788] ## [1.2-RC-SNAPSHOT] ## [-1.0.3-gamma+b7718] ## [+justmeta] ## [9.8.7+meta+meta] ## [9.8.7-whatever+meta+meta] ## [99999999999999999999999.9'; my $regex = qr/^##\s\[?(Unreleased)\]?|^##\s\[((0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?)\]$/mp; if ( $str =~ /$regex/g ) { print "Whole match is ${^MATCH} and its start/end positions can be obtained via \$-[0] and \$+[0]\n"; # print "Capture Group 1 is $1 and its start/end positions can be obtained via \$-[1] and \$+[1]\n"; # print "Capture Group 2 is $2 ... and so on\n"; } # ${^POSTMATCH} and ${^PREMATCH} are also available with the use of '/p' # Named capture groups can be called via $+{name}

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html