XEmacs still runs in lisp for me and I am not sure if it could be converted into perl before the universe ends but theoretically it can be done.

Time constrained problems sound like the biggest issue, for example Van Eck Phreaking or high quality real time audio synthesis would be challenging but on the other hand with a suitable C library and interesting hardware both might be within arm's reach. I am pretty sure though that I will not ride a rocket with an engine written in perl though.

I like wxPerl but I think it needs another layer of laziness proofing on top of it to be "insanely great", i.e. you still have to tell the pesky computer what to do. I tend to agree with you but perl would be closer to the insanely great end of the spectrum if it included some AI, natural language directed automatic code generation, whiz bang graphics, and free hardware. But it is still pretty great anyway.

Anyway don't let anyone tell you there is anything Perl can't do, it is probably just a matter of them not using strict.