By the way, for this sort of thing, understanding and using the concepts in this thread:
Altering functions without overwriting them is quite important.
If done right, it'll allow you to use the Lua on any map without breaking anything. If you overwrite an important function like startup, though, things could really break (or if you copy+paste a specific startup function then it'll only work for some maps).
It's still not a perfect system, and the base includes should be restructured to allow for easier/more robust manipulating, but that hasn't happened yet.