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

DESCRIPTION

perlre documents Perl regular expressions, one of the most powerful regex implementations. Perl's regex syntax influenced many other languages and tools (PCRE).

$ /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

MODIFIERS

$ /i  - Case insensitive
/g  - Global match
/m  - Multiline mode
/s  - Single line (. matches \n)
/x  - Extended (allow whitespace)
/o  - Compile once

Match and capture

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

$
# 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.

# SEE ALSO

perl(1), perlretut(1), perlreref(1), pcre(3)