while( my $r = $qr->dequeue ) {
    ++$count;

    if ($count == 63) {
        $t = time;
    }


##</code><code>##

    elsif (($count & 63) == 0) {
        if (time > $t + 5) {
            printf "%f\n", $count / ($N * $N * (time - $t));
            last;
        }
    }
}

##</code><code>##

perl -E"$s=time(); $i=0; ++$c, rand()*rand() while time() < $s+5; say $c/5"
3210038.8