wait
Waits for a child process to terminate and returns the
pid of the deceased process, or -1 if there are no child processes.
The status is returned in $?.
If you get zombie child processes, you should be calling either this function
or waitpid. A common strategy to avoid such zombies is:
$SIG{CHLD} = sub { wait };system, a close on a pipe, or backticks between
the fork and the wait. These constructs also do a
wait(2) and may have harvested your child process.
Use waitpid to avoid this problem.