Try not to get hung up on the "switch" issue. In my view given/when is a fine addition to the language, but it came bundled with the smart match operator. It turned out the smart match operator was a bad idea (much too powerful and arcane) and unfortunately, because it was bundled with given/when, given/when acquired the same bad rep. As eyepopslikeamosquito suggests, there are other ways to do it - and that is really a cornerstone of Perl: there are many ways to do most things so you can play around and see what works best for you and the task at hand.

Perl is a great language for this sort of task where you are munging files. But tricky stuff is tricky stuff and all a good language can do is make it easier to think about the key parts of the problem while it hides the boring stuff away. If someone else hasn't already done the job for you (or you can't find it) and you don't want to pay someone to do it, ya just gotta do the tricky stuff.