use threads;
use threads::shared;
use Thread::Queue;

my $a :shared;
$a = 0;
my $q = Thread::Queue->new();

sub set_positive {
	while (1) {
		lock $a;
		lock $q;
		if ($a == 0) {
			$a = int(rand() * 100);
			$q->enqueue($a);
			print "At set_positive: $a\n";
			sleep(1);
			cond_broadcast($a);
		} else {
			cond_wait($a)
		}

	}
}

sub set_zero {
	while (1) {
		lock $a;
		lock $q;
		if ($a > 0) {
			$a = 0;
			$q->enqueue($a);
			print "At set_zero: $a\n";
			sleep(1);
			cond_broadcast($a);
		} else {
			cond_wait($a)
		}
	}
}

sub printer {
	while (1) {
		lock $a;
		lock $q;
		my ($v_a, $v_b) = $q->dequeue(2);
		print "At printer $v_a $v_b ",$a, $/;
		sleep(1);
	}
}

my @threads = map threads->create($_), qw( set_positive set_zero printer);
$_->join for @threads;