use threads;

    $thr = threads->new(\&sub1); # Spawn the thread

    $thr->detach; # Now we officially don't care any more

    sub sub1 {
        $a = 0; 
        while (1) { 
            $a++; 
            print "\$a is $a\n"; 
            sleep 1; 
        } 
    }

##</code><code>##

threads->create("t_sub1")->detach();
threads->create("t_sub2")->detach();