use strict;
use warnings;

use threads;
use threads::shared;

my @stack: shared;

my $thr = threads->create(\&thr2);

threads->create(\&thr1)->detach;
threads->create(\&thr1)->detach;

$thr->join;

sub get {
    threads->yield while scalar @stack == 0;
    lock(@stack);
    pop @stack;
}

sub put {
    my $val = shift;
    lock(@stack);
    push @stack,$val;
}

sub thr1 {
    put($_) for 1..500;
}

sub thr2 {
    my $cnt;
    my $val;

    while ($val = get()) {
        $cnt++;
        print "$val ($cnt)\n";
    }
}