Why don't it print ?

[velinas]

Hi all,
why don this littly thingy work? It should print, sleep and after sleep print again 
but it does print both at same time. Not one before sleep and one after. I tried:

while ($i < 10)
    {
    print'sleep...';
    sleep(10);
    print" done\n";
    }

Anyone can help me with that?
Thx! :)