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!