I implemented something that sounds very similar with Net::Pcap and NetPacket.

In general, I read the documentation available on CPAN for the modules, see which one seems to come closest to what I want, then try it and see if it actually works. I'll also poke around inside the code a bit to see if I can extend it and fix bugs if I need to. If I'm not happy with the first one, I'll try the next. Choosing the right modules to build your code on top of is a really important decision, and you should expect to spend a moderate amount of time researching and testing.