if( my $pid = fork() ){
    print "parent ($$) is waiting on child $pid\n";
    my $kid ;
    do {
        $kid = waitpid(-1, WNOHANG);
    } while $kid > 0;
    my $exit = $? >> 8;
    die qq{Kid ($kid) exited with $? / $exit \n};
} else {
    print "I am the kid $$\n";
    sleep 1;
#~     exit 666; ## too big
    exit 12;
}
__END__
parent (1724) is waiting on child -880
I am the kid -880
Kid (-880) exited with 3072 / 12