friedo and EvanCarroll are right that index will probably be fastest. Still, I wanted to clarify that by using =~, you're using a regex; that's exactly what the =~ operator does. You can learn more about regular expressions in the perlre(1) manpage included with Perl, in any good book on Perl (such as Learning Perl or Programming Perl), or in the O'Reilly book Mastering Regular Expressions.