use POSIX ":sys_wait_h";
sub REAPER {
    my $child;
    # If a second child dies while in the signal handler caused by the
    # first death, we won't get another signal. So must loop here else
    # we will leave the unreaped child as a zombie. And the next time
    # two children die we get another zombie. And so on.
    while (($child = waitpid(-1, WNOHANG)) > 0) {
        $Kid_Status{$child} = $?;
    }
    $SIG{CHLD} = \&REAPER; # still loathe SysV
}
$SIG{CHLD} = \&REAPER;
# do something that forks...