my $LIFETIME_THREADS=100;
while (! $TERM) {
  for (my $needed = $MAX_THREADS - threads->list();
          $needed && ! $TERM;
          $needed--) {
    # New thread
    threads->create('worker', $queue, $TIMEOUT) if ($LIFETIME_THREADS-- >0);
    exit(0) if (threads->list()==0);
  }
  # Wait for any threads to finish
  sleep(1);
}