Simple iterator with ruby fibers

I wanted to do someting simple with fibers to see how the basics work so that's what I came up with. Forgive my C-ish 'while' syntax. I haven't written it like this for way too long. I just had too.

https://gist.github.com/depy/5843359#file-gistfile1-txt

(For some reason I can't use @ in code in markdown. No idea how to fix this so I pasted the code in github gist.)