Nested functions, how do they work (stack related)

[Veek M]

http://web.archive.org/web/20111030134120/http://www.sidhe.org/~dan/blog/archives/000211.html
(great tail recursion article - best i've seen! SO doesn't really 
explain it unless you already knew it to begin with, but here's the 
link:http://stackoverflow.com/questions/310974/what-is-tail-call-optimization)

I found it useful to read because it deals with the stack. Basically 
when an exception occurs you need to mess with the stack so..