The fundamental difference is that Perl doesn't think itself beautiful. There's plenty to hate specific to Perl: sigils for types, noisy syntax (not even the #$@%, just the structure is ugly), nested lists always being flattened silently (as a design choice, Larry is crazy).

I never end up using Perl, the niche it occupies between shell and python is empty for me. I never have a problem with a shell script where I'm wishing for more control structures or builtins. The few times I've written long-running resource-intensive shell scripts (like brute-forcing an MBR partition scheme), reducing the number of forks wouldn't make them more than a few percent faster.

The major ray of light shining down on Ruby is that it is a Perl that people want strongly to write better looking code in. That's a pretty big accomplishment, I think. It seems like a lot of the classic Perl webdev shops are moving to Ruby, and I think that's pretty great.

I don't hate Ruby, I'm just disappointed in it.