The correct way to write that loop

    while( @arrayRunningThreads ){
        my @keepers;
        for my $thread ( @arrayRunningThreads ){
            if( $thread->is_joinable() ){
                $thread ->join;
            } elsif( not $thread ->is_detached ){
                push @keepers, $thread;
            }
        }
        @arrayRunningThreads  = @keepers;
    }
[download]

If you don't add detached threads you can write it as

    while( @arrayRunningThreads ){
        my @keepers;
        for my $thread ( @arrayRunningThreads ){
            if( $thread->is_joinable() ){
                $thread ->join;
            } else {
                push @keepers, $thread;
            }
        }
        @arrayRunningThreads  = @keepers;
    }
[download]

Or the functional equivalent of what the above code does, relying on the fact that join blocks until a thread is_joinable

    for my $thread ( @arrayRunningThreads ){
        $thread->join;
    }
[download]