Proc::Wait3 module implements wait3 system call in Perl.
If any child processes have exited, this call will "reap" the zombies
similar to the perl "wait" function.  By default, it will return
immediately and if there are no dead children, everything will be
undefined. If you pass in a true argument, it will block until a child
exits (or it gets a signal).

WWW: http://search.cpan.org/dist/Proc-Wait3/