Regular Expressions

• Perl regular expression features borrowed by Java, C#, and other languages

• Sample regular expression to match an IP address: \d{1,3} ( \. \d{1,3} ){3} 1-3 digits followed by 3 more groups of 1-3 digits each preceded by a period

• Sample usage: if ( ! $input =~ /^\d{1,3}(\.\d{1,3}){3}$/ ) { die "Sorry, $input is not an IP address\n"; }