It's a bit hard to give real answers to your question, as different flavours of Unix act differently. I'd suggest to carefully study your system manuals about signals, signal handlers (and their need to be reinstalled), fork and the various wait calls.

One code suggestion I'd like to make. Consider using waitpid instead of wait. perldoc -f waitpid contains a code fragment you may want to use: a non-blocking loop that reaps all zombied children.

Abigail