use threads;
use threads::shared;

our $MAX ||= 10;

$|++;

my @threads;
while( 1 ) {
    push @threads, threads->create( sub{ 1; } ) while @threads < $MAX;
    printf "\rCreated so far; %d\t", $threads[ -1 ]->tid;
    $_->join for @threads;
    @threads = ();
}