This actually uses index, so it should run faster than regex based versions.

Not necessarily. If the text is a simple string, the regex engine can kick in BoyerMoore and other optimizations, and actually beat a naive index operation. Having said that, I believe that modern Perls actually hand index to the regex engine, just so that it can use BoyerMoore!

-- Randal L. Schwartz, Perl hacker