perl 多进程调用

use POSIX;



foreach my $id(sort keys %serv)
{
my $pid=fork();
        if($pid==0)
        {
                alarm(10);
                qq#$cmd#;
                alarm(0);

                exit;
        }
        else
        {
                $chd_pid{$pid}=0
        }
}
#等待回收子进程
while (scalar (keys %chd_pid))
{
        my $pid = 0;
        $pid=waitpid(-1, NULL);
        if (exists $chd_pid{$pid})
        {
                print "pid =  $pid \n";
                delete $chd_pid{$pid};
        }
}