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

Substitution

Processing...

Code Generator

Language

Generated Code

use strict; my $str = 'reflectance_7_myd21a1_emissivity_29 reflectance_7_myd21a1_emissivity_29_savitzkygolay reflectance_7_myd21a1_emissivity_31 reflectance_7_myd21a1_emissivity_31_savitzkygolay reflectance_3_myd21a1_emissivity_32 reflectance_2_myd21a1_emissivity_32_savitzkygolay reflectance_1_mcd43a3_albedo_bsa_band1 reflectance_3_mcd43a3_albedo_bsa_band2 reflectance_7_mcd43a3_albedo_bsa_nir reflectance_7_mcd43a3_albedo_bsa_shortwave reflectance_7_mcd43a3_albedo_bsa_vis reflectance_7_mcd43a3_albedo_wsa_band1 reflectance_7_mcd43a3_albedo_wsa_band2 reflectance_7_mcd43a3_albedo_wsa_nir reflectance_7_mcd43a3_albedo_wsa_shortwave reflectance_7_mcd43a3_albedo_wsa_vis'; my $regex = qr`(^reflectance_\d_)(\S*)$`mp; my $subst = '($1)vs_$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