[Warning: Viewers who do not want to see an extremely geeky post, look away now.]
Colour me impressed with POE. POE is an event-based object environment for Perl. It provides a framework to handle messaging between different processes, and allocation of processor time -- so, for example, it's very good at doing server based things. And the interfaces are designed really well. I managed to hook it into a different event handler, and effectively deal with incoming requests quite happily with my first script, in one attempt. That's after only one evening browsing through the documentation.
Resource to peruse come down to two. A Beginner's Introduction to POE covers the introduction and some sample scripts (it's essentially the POE manpage). For more in depth information, check out the POE Wiki for documents (POE::Kernel and POE::Session is probably all you'll need), and Cookbook scripts. For multiuser, interactive Perl applications, I reckon this is where it's at.
[Viewers, you may now open your eyes.]