perlre
documents Perl regular expressions, one of the most powerful regex
TLDR
View Perl regex documentation
$ perldoc perlre
View quick reference$ perldoc perlreref
View regex tutorial$ perldoc perlretut
View character classes$ perldoc perlrecharclass
SYNOPSIS
perldoc perlre
DESCRIPTION
perlre documents Perl regular expressions, one of the most powerful regex implementations. Perl's regex syntax influenced many other languages and tools (PCRE).
BASIC PATTERNS
$ /pattern/ # Match
s/old/new/ # Substitute
m/pattern/i # Case insensitive
/pattern/g # Global
# Character classes
\d - Digit
\w - Word character
\s - Whitespace
. - Any character
s/old/new/ # Substitute
m/pattern/i # Case insensitive
/pattern/g # Global
# Character classes
\d - Digit
\w - Word character
\s - Whitespace
. - Any character
MODIFIERS
$ /i - Case insensitive
/g - Global match
/m - Multiline mode
/s - Single line (. matches \n)
/x - Extended (allow whitespace)
/o - Compile once
/g - Global match
/m - Multiline mode
/s - Single line (. matches \n)
/x - Extended (allow whitespace)
/o - Compile once
CAPTURES
$ # Match and capture
if ($text =~ /(\d+)/) {
print "Found: $1\n";
}
# Named captures
/(?<name>\w+)/;
print $+{name};
# Non-greedy
/.*?/
if ($text =~ /(\d+)/) {
print "Found: $1\n";
}
# Named captures
/(?<name>\w+)/;
print $+{name};
# Non-greedy
/.*?/
ADVANCED FEATURES
$ (?:...) - Non-capturing group
(?=...) - Positive lookahead
(?!...) - Negative lookahead
(?<=...) - Positive lookbehind
(?<!...) - Negative lookbehind
(?>...) - Atomic group
(?=...) - Positive lookahead
(?!...) - Negative lookahead
(?<=...) - Positive lookbehind
(?<!...) - Negative lookbehind
(?>...) - Atomic group
CAVEATS
Complex regex can be slow. Use /x for readability. PCRE differs slightly from Perl regex.
HISTORY
Perl regular expressions were designed by Larry Wall and evolved through Perl versions, becoming the standard for modern regex.