Some years ago I learned of existence of (supposedly cool) POE framework for Perl. I tried to use it for some projects, but the learning curve proved to be fatal for my interest.
All the time I felt that POE is great, it's just that I'm too stupid to be able to actively use it.
Time passed by. Something like half a year ago, friend asked me if it would be possible for me to write a cool program – HTTP proxy for their MUD.