use bignum;
    use v5.10;

    =cut
    def Factorial(x):
      output = 1
      for i in xrange(x):
        output *= (i + 1)
      return output
    =cut


    # Direct translation
    sub factorial {
      my $x = shift;
      my $output = 1;
      for my $i (1 .. $x) {
        $output *= $i;
      }
      return $output;
    }

    say factorial(200);

    =cut
    def Factorial2(x):
      return reduce(operator.mul, xrange(1, x + 1), 1)
    =cut

    use List::Util "reduce";

    sub factorial2 {
      my $x = shift;
      reduce { $a * $b } (1 .. $x);
    }

    say factorial(200);

    =cut
    def Power(a, b):
      if not b:
        return 1
      if b % 2:
        return Power(a, b - 1) * a
      x = Power(a, b/2)
      return x * x
    =cut

    sub power {
      my $a = shift;
      my $b = shift // return 1;
      
      if ($b % 2) {
        return power($a, $b - 1) * $a
      }

      my $x = power($a, $b/2);
      return $x * $x;
    }

    # lambda x: x + 7
    my $plus7 = sub { $_[0] + 7 };
    # Or:
    my $plus7 = sub { my $x = shift; $x + 7 };

    say $plus7->(14);

    =cut
    def TweakValue(x):
      return x + 7
    =cut

    sub plus7 { $_[0] + 7 }
    say plus7(14);