It would be quite a large problem for almost anything real-life related.
Ruby GEMS are nowhere near CPAN's breadth, how would you feel when you discovered that your language of choice needs creating from scratch SSL bindings, jabber, MS SQL library, bittorent etc etc?
It's not important as long as you're living close to university, but these days, when protocols are as complicated as bittorent's or skype's, you have very little choice.
Some people say Haskell is great
"faster than C++, more concise than Perl, more regular than Python, more flexible than Ruby, more typeful than C#, more robust than Java, and has absolutely nothing in common with PHP."
, I found scheme quite to my liking, but if I would like to replace perl with them, I would have to start with taking few years off, to recreate important parts of perl toolkit.