hamming perlesque

my $three = BigInteger.Parse("3");
my $five = BigInteger.Parse("5");

sub updateFrontier(BigInteger $value, SortedSet[BigInteger] $frontierSet) {
    $frontierSet.Add(BigInteger.op_LeftShift($value, 1));
    $frontierSet.Add($value * $three);
    $frontierSet.Add($value * $five)
}

sub getHammingNumbers(int $howMany, boolean $all --> List[BigInteger]) {
    my $completedNumbers = List[BigInteger].new;
    if ($howMany == 0) {
      return $completedNumbers;
	}

    my $frontierSet = SortedSet[BigInteger].new;
    $completedNumbers.Add(BigInteger.One);
    updateFrontier(BigInteger.One, $frontierSet);
    my $count = 1;
    while ($count < $howMany) {
        my $lowestNumber = $frontierSet.Min;
        $frontierSet.Remove($lowestNumber);
        if ($all) {
            $completedNumbers.Add($lowestNumber)
        } else {
            $completedNumbers[0] = $lowestNumber;
        }
        $count++;
        updateFrontier($lowestNumber, $frontierSet);
    }
    return $completedNumbers
}

say "First 20 Hamming numbers: ";
my $twenty = getHammingNumbers(20, true);
loop (my $i=0;$i<$twenty.Count;++$i) { say $twenty[$i] }
say "1691st Hamming number: " ~ getHammingNumbers(1691, false)[0];
say "One millionth Hamming number: " + getHammingNumbers(1000000, false)[0]