perl 
-Mthreads="stack_size,4096" 
-Mthreads::shared 
-MTime::HiRes=time 
-wE"
    $N = 64;
    $t = time;
    my$c :shared = 0;
    async( sub{ ++$c; sleep 10 } )->detach for 1..$N;
    1 while $c < $N;
    say time-$t;
    sleep 10
"
0.578999996185303

perl 
-Mthreads="stack_size,4096" 
-Mthreads::shared 
-MTime::HiRes=time 
-wE"
    $N = 256;
    $t = time;
    my $c :shared = 0;
    async( sub{ ++$c; sleep 10 } )->detach for 1..$N;
    1 while $c < $N;
    say time - $t;
    sleep 10
"
2.57699990272522