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

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

sub set_positive {
    while (1) {
        lock $a;
        if ($a == 0) {
            $a = 1+int(rand() * 100); ## Modified 10/03/2016 15:57 in accordance with 1156654 & 1157305
            $q->enqueue($a);
            print "At set_positive: $a\n";
        } else {
            cond_wait($a)
        }
        cond_broadcast($a);
    }
}

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

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

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