#!/usr/bin/perl -w
 # prime-pthread, courtesy of Tom Christiansen
 use strict;
 use Thread;
 use Thread::Queue;
 my $stream = new Thread::Queue;
my $kid    = new Thread(\&check_num, $stream, 2);
for my $i ( 3 .. 1000 ) {
    $stream->enqueue($i);
} 
$stream->enqueue(undef);
$kid->join();
sub check_num {
    my ($upstream, $cur_prime) = @_;
    my $kid;
    my $downstream = new Thread::Queue;
    while (my $num = $upstream->dequeue) {
 next unless $num % $cur_prime;
 if ($kid) {
           $downstream->enqueue($num);
 } else {
 print "Found prime $num\n";
     $kid = new Thread(\&check_num, $downstream, $num);
 }
    } 
    $downstream->enqueue(undef) if $kid;
    $kid->join()		if $kid;
}