If you're on Linux, forking is probably more efficient than you think it is. You'd have to be doing almost nothing in your actual processing for it to have a big impact.

If you're determined to have the most efficient approach possible, it would most likely be a single process using non-blocking I/O. There are some event modules on CPAN, like Event-Lib. At the point where you are worried about the overhead from forking though, you probably should be looking at C.