app needs perl but each updates require blowing away perl and reinstalling their stuff new

If updates to their product actually require blowing away core Perl, then their product is set up incredibly badly. Furthermore if their product is set up that badly, then sight unseen I can guarantee you that they've screwed enough other things up that their product is shite.

I'll put my reputation as a Perl programmer behind that.

Given the situation that you describe, I'd suggest installing another copy of Perl that their crap doesn't even know about, let alone touch, and then install all of the binary modules that you want on that copy of Perl. If possible, I'd suggest making them use the private copy of Perl. But if they are already screwing with core Perl, then odds are that they don't have the good taste to understand that core Perl might not be exactly where they expect.

Are you sure that you haven't misunderstood something about the situation? If you do understand correctly, then can you convince the powers that be that they should use something that is a bit better designed than this?

Cheers,
Ben

That way you can install whatever you want and not sweat it if, for instance, you need a driver with some binary bits.

Cheers,
Ben