Windows doesn't do zombie processes.

However, perl attempts to emulate the ability to retrieve the exit code from child processes by storing them within the parent, from where they can be retrieved using wait and $? or waitpid.

A side effect of this is that you can only start 64 child processes before you must free up slots in a perl internal structure by calling one of wait or waitpid. If you are starting less than 64 processes, you can happily and economically ignore this caveat.