use threads;
use Thread::Queue;

my $WQ = Thread::Queue->new('unit001' .. 'unit123');
sub qrun {
    map { $_ ? (worker($_), qrun()) : () } $WQ->dequeue_nb;
}
sub worker {
    warn "Work $_";
    select(undef, undef, undef, rand 3);  # sleep some
    return "$_!";
}

print for
map { $_->join } map { threads->new(\&qrun) } 1 .. 15;