If speed is a significant factor, then Perl probably isn't your best language.

In fact, if any of the modules get a speed up, it's probably because they're using compiled parts. They would actually have more overhead, because they need to be made more generic so that they can be applied to generic uses, and to deal with problem input that might not be a factor in your situation.

It may be possible to get a speed up by streamlining the logic of your program, or by trading off memory or disk for speed.

From what you'r describing, in dealing with legacy code that's difficult to maintain, I'd suggest the Perl Medic book, even if the front page to the site is rather horrible.