Select Code to Download

>perl -MPOSIX=:sys_wait_h -le"my $pid = system 1, $^X=>(-e=>'sleep 5')
+; while (waitpid($pid, WNOHANG) == 0) { print 'waiting'; sleep 1; } p
+rint 'done'"
waiting
...
waiting
waiting
done

use POSIX qw( WNOHANG );

...
    die("waitpid: $!\n") if $rv == -1;
    return $rv;
}