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

/
/
gm

Test String

Code Generator

Generated Code

use strict; my $str = '# This is currently a test {nav Home} The statistical model estimated the probability, {tex f(x) = \\int_{-\\infty} ^\\infty \\hat f(\\xi)\\,e^{2 \\pi \\xi x} \\,d\\xi }, of capturing dolphins on a tow, {tex i}. A year effect, {tex \\lambda_{acb_{j}}} was estimated for each year, {tex j}, allowing for annual variation in the capture event rates that was unrelated to the covariates, {tex x}. The contribution of each covariate, indexed by {tex c}, was governed by a regression coefficient, {tex \\beta_c}, that was estimated by the model. The logit transform of the capture event probability was defined as the sum of the year effect, {tex \\lambda_{lam} {lam} }, and the covariates: {tex \\lambda_{lam}{lam} } {tex \\lambda_{lam} {lam} } {tex \\lambda_{lam}{lam}} katex {{{ logit(\\pi_i) = \\lambda_{j[i]} + \\sum_c \\beta_c x_{ic}. }}} determines the result. # The following is more tests katex {{{ f(x) = \\int_{-\\infty}^\\infty \\hat f(\\xi)\\,e^{2 \\pi i \\xi x} \\,d\\xi }}} katex {{{ \\begin{bmatrix} a & b \\\\ c & a \\end{bmatrix} }}} katex {{{ \\begin{bmatrix} a & c \\\\ c & a \\end{bmatrix} }}} '; my $regex = qr/{tex\b([^{}]*({[^{}]*?([^{}]|(?R))*[^{}]*?}[^{}]*)*[^{}]*)}/mp; 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