Regular expressions with potentially zero-width wildcards (especially .*) can be exceedingly slow. If someone claims Perl is slow because it handles a difficult regular expression with due care, then that simply shows a lack of understanding on their part. Perl contains a regular expression engine, as do many other languages--but regular expression syntax is a language unto itself.

Part of the advantage of using a module is that you get to take advantage of the effort someone else has gone to to get the regular expression right and (hopefully) efficient.