It does not do anything with $thr.

Exactly. You are throwing it (them, one for each thread you create) away. So don't do that, save them.

my @threads;
for (0 ..3)) {
    my $thr = threads->create( 
        sub { worker(); } 
    );
    $thr->detach();
    push @threads, $thr;
}

... # then later
for my $thr ( @threads ) {
    print 'Thread ', $thr->tid, 
        $thr->is_running ? ' is running' : ' is not running';
[download]

I did something similar: and I get this message. <bolckquote> Can't locate auto/threads/is_running.al in...

foreach my $test (@all_threads)
{
        if( $test->is_running() )
        { print "Running: $test\n"; }
}
[download]

Which version of threads are you using?

So, maybe you want to do something with $thr, then, if you want to monitor the newly created thread? The threads documentation lists various uses for the return value of ->create(). Maybe now is a good time to read that documentation and look for these uses.

Also, again, maybe you really don't want to ->detach threads but to just keep them around and ->join them. Just feed them from a Thread::Queue and wait until they have all finished as all work has been done. But then, I'm sure that approach has already been shown to you.

I don't need the workerThreads to wait at all, I just want them in while loop and keep reading from DataQueue, and MasterThread to Just Queue to DataQueue.

My only concern was to watch and make sure all workerThreads are alive.

So, I don't know if I can use join() in my case

Maybe now is a good time to review the threads documentation. The skeleton for a simple Thread::Queue worker approach is outlined by BrowserUk in 735931. Maybe you want to work from that, or do some more research into other posts on the subject on this site.