use Thread::Queue;
#
#    Thread::Queue is already shared (in fact, 
#    its just a shared array)
#
our $queue = Thread::Queue->new;

sub thread_sub {
     while ($test == 0) {
         if (certain test is true)
             {$test = 1;}
     }
#
#   Not certain of your intent here, but assuming you're
#   just trying to send some data to another thread, then
#   you just need to pass the data as a parameter;
#   Note that doing so will return immediately wo/
#   any ack. from the recv'r. Also note that
#   if $action is a ref to something, then that
#   something must also be threads::shared
#
#     {my $action = $queue->enqueue;}
     $queue->enqueue($action);
}

sub thread_sub1 {
#
#    this is fine.
#
      $action = $queue->dequeue; #??? totally lost here
      print "I am going to do your bidding master now that the test is
+ true\n";
}
[download]

If you need full duplex communications between threads, you might peek at Thread::Queue::Duplex or Thread::Queue::Multiplex.

Thanks for your response. I dont even want to pass data to the other threads - I just want them to start moving at the calling of the first threads.

Does the code need to change at all if looped as the original example suggests?

Brian