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

/
/
gi

Test String

Code Generator

Language

Generated Code

use strict; my $str = '<meta name="keywords" content="keyword1, keyword2, keyword3"> <a href="something" onclick= "bad()">text</a> onclick not in tags <a href="something" onclick =bad()>text</a> <a href="something" onclick=bad(\'test\')>text</a> <a href="something" onclick=bad("test")>text</a> <a href="something" onclick="bad()" >text</a> <a href="http://mydomain.com/index.php?oninaval=12" class="titi">text</a> What if I write john+onelia=love forever? <a href="something" onclick="bad()">text</a> onclick not in tags <a href="something" onclick=bad()>text</a> <a href="something" onclick="bad()" >text</a> <a href="something" onclick=a++ >text</a> onclick="asd <span class="myclass"> not in tag too.</span> <!-- onclick=" --><a href="something" onclick= "bad()">text</a> <textarea><enter onclick="dothat()" text here></textarea> yoko ono="john lennon" <img src="/images/img1.jpg" alt="onclick=thegood() onclick=thebad() "/> <img alt="onclick=" src=/images/theugly.jpg> the most important part of the message <p class="disappears"></p> <a href="" onmouseover=a=7>button1</a> <a href="something" onclick=a++>text</a> <a href="something" onclick=a<<1>text</a> <a href="" onmouseover="alert(a);">button2</a>'; my $regex = qr/(<.+?)(?<=\s)on[a-z]+\s*=\s*(?:(['"])(?!\2).+?\2|(?:\S+?\(.*?\)(?=[\s>])))(.*?>)/ip; 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