BTW, I love the idea.

My comment on portability:
As I have to work on a Windows machine, the "$^X" statement is what is working for me, there is no `which` here. Well, here is one now, but that only finds perl.exe not perl.

The File::Which is working on NT, it includes a pwhich, which would do the job, but then you have a dependence on possibly not installed modules.