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

Substitution

Processing...

Code Generator

Language

Generated Code

use strict; my $str = 'U.S.A. is the country? i want to live in. if you please. yes. nope. U.S.A. is the country? i want to live inc. if you pease. dope. yes. U.S.A. is the country? i want to live Inc. if you pease. dope. yes. u.s.w. and so on. a German abbreviation. U.s.w. and so on. a German abbreviation. // str // .replace( // (/(?<!\\b(?:inc|pease|nope|U.S.A|u.s.w))([.?!]\\s+)(\\w)/gi), // (_, $1, $2) => $1 + $2.toUpperCase() // ); // ... or ... // str // .replace( // (/(?<!inc|pease|nope|U.S.A|u.s.w)([.?!]\\s*)(\\w)/gi), // (_, $1, $2) => $1 + $2.toUpperCase() // ) // .replace((/U\\.S\\.W\\./g), \'u.s.w.\'); '; my $regex = qr/(?<!\b(?:inc|pease|nope|U.S.A|u.s.w))([.?!]\s+)(\w)/ip; my $subst = '$1$2'; 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