Detecting thread exits

[Eric Garland]

I'm setting up a Boss/Worker threaded program that runs for a very 
long time.  There are times where a worker thread will run into errors 
and exit.  The obvios solution would be to prevent that from happening 
but I would like to create a fault tolerant framework that doesn't tip 
over at the slightest hint of a problem.  I would like to have the 
Boss detect when a worker exits and restart a worker thread in its 
place.

So far, I find no functions that will determine if a thread has exited 
outside of join().  The obvious issue with join is that it blocks so I 
need a join thread for each worker thread so that I can send a message 
back to the Boss to restart the thread.  This seems to wildly increase 
the memory usage.   There are large shared data structures in this 
program and it already seems to be at the memory limits of the machine 
without these join threads.

Is there a way to remove the shared variables from the join threads so 
that they take up as little memory as possible?

Better yet, is there a way to detect thread deaths outside of a 
dedicated join thread, perhaps a $thread->ready_for_join() type 
function or a $thread->join_non_blocking() or even a 
$thread->join_any_of_these(@threads)?

Thanks
	-Eric