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

~
~
g

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

use strict; my $str = 'The problem is, if the page contains a PDF linked to another page (not my own website), example https://othersite.example.com/whatever.pdf, it becomes https://othersite.example.com/whatever_SPANISH.pdf which isn\'t valid on other people\'s sites. I want to ignore offsite links and only change URLs on my site. So what I would like to do is look for the string: https://example.com/documents/en/whateverfilename.pdf and pull that file name out and change it to https://example.com/documents/es/whateverfilename_SPANISH.pdf (Switching the en to es and also appending the _SPANISH to the end of the PDF filename. '; my $regex = qr~\b(https?://[^\s/]+/documents/)en/([^\s/]+)\.pdf\b~p; my $subst = '$1es$2_SPANISH.pdf'; my $result = $str =~ s~$regex~$subst~rg; print "The result of the substitution is' $result\n";

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