Python had to go through a lot of pain for that, the "nonlocal" keyword was only added in Python 3.0, and the local/global distinction is very fragile.

Javascript and Coffeescript try to solve this in different ways, most people think that JavaScript's method sucks, and many are not fond of CoffeeScript's non-locality. Personally, I think that demanding variable declaration is still the best option (possibly except for interactive sessions).