It doesn't look like Ruby has tail-call optimization, either. Lua does...what other primarily-scripting (i.e., not Scheme or Haskell) languages do?

    # Ruby 1.8.7
    def Y
      lambda { |f| f.call(f) }.call(
        lambda do |g|
          yield(lambda { |*n| g.call(g).call(*n) })
        end)
    end
    Y { |this| lambda { |n| n == 0 ? 1 : n * this.call(n - 1) } }.call(5)
    #=> 120

my $factorial = sub (Int $x) { $x < 2 ?? 1 !! $x * &?ROUTINE($x - 1); }