my $sub;
$sub = sub {
  my $num = shift;
  if (0 == $num) {
    return 1;
  }
  else {
    return $num * $sub->($num - 1);
  }
};
print $sub->(5), "\n";
print $sub->(6), "\n";

##</code><code>##

function (builder) {
  return function (n) {
    return builder(builder)(n);
  }
}(
  function (recurse) {
    return function (n) {
      if (0 == n)
        return 1;
      else
        return n * recurse(recurse)(n);
    };
  }
)(
  5  // THIS is the factorial to compute
);