my @primes = gather {
        my sub prime(Int $n) {
                for @primes -> $d {
                        last if $d*$d > $n;
                        return 0 if $n%$d==0;
                }
                return 1;
        }
        my Int $next = 1;
        while ++$next {
                take $next if prime($next);
        }
};