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

/
/
gs

Test String

Code Generator

Language

Generated Code

use strict; my $str = '<!DOCTYPE html> <html> <head> <title>Hyperlinks</title> <link href="theme.css" rel="stylesheet" /> </head> <body> <ul><li><a href="/" id="home">Home</a></li><li><a class="selected" href="/courses">Courses</a> </li><li><a href = \'/forum\' >Forum</a></li><li><a class="href" onclick="go()" href= "#">Forum</a></li> <li><a id="js" href = "javascript:alert(\'hi yo\')" class="new">click</a></li> <li><a id=\'nakov\' href = http://www.nakov.com class=\'new\'>nak</a></li></ul> a href="#empty"></a> <a id="href">href=\'fake\'<img src=\'http://abv.bg/i.gif\' alt=\'abv\'/></a><a href="#">&lt;a href=\'hello\'&gt;</a> <!-- This code is commented: <a href="#commented">commentex hyperlink</a> --> </body> '; my $regex = qr/(?<=<a)(.+)\s?href\s*=\s*("|')(.+?)(\2)/sp; 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