C is quite (but not entirely) unlike Perl. You may not have to learn all the little details, but learning enough to write some minimal code wrapper is a good idea.

When you're coding on a regular basis, sooner or later you'll come across some half-arsed hardware you want to access (either because it's cool or your boss tells you so) and the only "easy" way is to write an XS wrapper for the propritary library that came with it. If you know a little C, it's not that hard - you'll have to struggle with MakeMaker for a few hours, but it wont be that hard to accomplish.

...that reminds me: note to $self: i still have to deliver on the promise to write a simple step-by-step Meditation on how to actually do this...

Learning SQL is also a very good, non-exclusive choice. It will help you quite a lot when dealing with large, complex sets of data.

Believe it or not, using databases is also quite fun... can't believe i just said that, maybe it's nearly time to go on vacation and do another bicycle trip?