I do about equal amounts of Perl and Ruby (neither as the core of what I do to eat) and generally agree with what graff has posted above. I stay away from Python because of the indentation thing, but I suspect I'm going to have to deal with it more soon. I probably wouldn't do a lot of Ruby if it weren't for Rails (and the various good and bad that comes with it)-- it's an easy way to get a site up fast, and Spree is easy to set up a store with and easy to modify, particularly if you're only doing it infrequently but want to do some non-standard web store things. If I need a quick hack for something, I go to Perl first (or C if I need a low level language).

As far as CPAN vs various Ruby gems, there's no comparison. Not only does CPAN have incredible depth and ease of finding useful modules, but they play very well together. I can't remember the time I tried to do something and had a conflict between module versions in Perl, but it seems like gem dependency version conflicts show up any time you try to do anything.

The prevalence of conflicts in Ruby gems is also a symptom of another major difference- Perl (at least 5.X) is a much more stable language as far as things like syntax and structure. The Ruby community (or parts of it) seem to fall prey to the "ooh, this is a cuter syntax, lets deprecate the old one!" a little too easily, and when you get forced into upgrading your Ruby you tend to have to go fix up a bunch of things that have been dropped since you last touched the code. It might be good job security for some people, but I mostly code because I need to get stuff done and I don't want to have to go back and rework stable code because someone decided to change the hash syntax.