I'm currently a Java programmer, but I was wanting to play around in scripting languages because I've never really used them. I don't really have a use for them right now, but I have some free time and I'd like to learn.

My picks were Lua, Python, Perl and Ruby. I wasn't really sure which one to learn though. Can anyone point out the differences or pros/cons to each of the languages and help me decide which one to try?