Global Var Disappearing After Function

Hey list, I have a very odd problem which has been driving me crazy for two days. I've been trying to debug my code and gave up. I finally coded a very simple representation of what the code does, and I get the same problem. However, I still don't understand what's causing it. The representational code: http://pastie.org/private/fz3lgvsjopz3dhid8cf9a As you can see, it's very simple. A variable is set, then a function is called which modifies the variable in the global scope. However, the modifications CANNOT BE SEEN after the function is called. The output from the script is here: http://pastie.org/private/29r5mrr1k7rtqmw7eyoja As you can see, the modifications in do_test() cannot be seen after the function is called. What is causing this? And how can I fix it? Thanks!