It really depends on whether you want to actually open each file in the perl program itself, or let the OS do that for you. I do something similiar to the latter, where I make a system call:
system ("sed 's/$searchString/$replacementString/g $filename > $newFilename'");
Note that I'm creating a NEW file with the changed text and not overwriting the original.
If you give a man a fish he will eat for a day.
If you teach a man to fish he will buy an ugly hat.
If you talk about fish to a starving man, you're a consultant.