my $thread1 = threads->create ( \&worker, 1, 'sub1.log' ); 
my $thread2 = threads->create ( \&worker, 2, 'sub2.log' ); 

my $need_to_continue = 1;
while ($need_to_continue) {
    print "MAIN THREAD IS PRINTING\n";
    if ( $thread1->is_running() || $thread2->is_running() ) {
        sleep 3;
    } else {
        $need_to_continue = 0;
    }

}

$thread1->join();
$thread2->join();

exit 0;