Eric Campbell Oct 06, 2025 0 min read Perl

Perl Regular Expressions: Still the Gold Standard

Perl's regex engine remains the most powerful text processing tool available. Here are patterns worth knowing.

Key Insights

Named captures (?…) make complex patterns self-documenting
Non-greedy quantifiers (*?, +?) prevent over-matching in nested structures
The /x flag allows whitespace and comments inside patterns for readability

Named Captures

my $log = '2024-01-15 ERROR [auth] Login failed for user@example.com';

if ($log =~ /(?<date>\d{4}-\d{2}-\d{2})\s+(?<level>\w+)\s+\[(?<module>\w+)\]\s+(?<msg>.+)/) {
    say "Module: $+{module}, Level: $+{level}";
}

Extended Mode for Readability

my $email_re = qr/
    (?<user>   [a-zA-Z0-9._%+-]+)   # local part
    @
    (?<domain> [a-zA-Z0-9.-]+)       # domain
    \.
    (?<tld>    [a-zA-Z]{2,})         # top-level domain
/x;

Lookahead and Lookbehind

# Password: at least one digit and one uppercase, 8+ chars
my $valid = $password =~ /^(?=.*\d)(?=.*[A-Z]).{8,}$/;