gistfile1.txt

        my $sched = ThreadPoolScheduler
            .new( :max_threads($!threads) );

        my $supply = $items.values.Supply;
        $supply.schedule-on($sched);

        my $i = 1;
        $supply.tap(
            sub ($item) {
                $sub($item);
                $prog.update($i++);
            }
        );
        $supply.done;
        $prog.message($msg);