About the only things to add from the other "evils of early optimization" comments,

A c function call takes less CPU then a Perl call.

After 15+ years of C coding, I wouldn't take that as gospel. I've seen too many poorly implemented c functions. If your c function is finely crafted then maybe its true for certain cases.

And the other addition ... optimization of my coding time is key nowadays and perl definetly has the one up there.

-derby