Splitting Lua scripts

[<thomas.heidenreich@...>]

I am working since a few days with the program FEMM and I am not very familiar with the scripting language lua. I have a little problem: I wrote a quite big lua script file and want to split it into multiple little lua script files in order to make it more orderly. But how? Here my questions: 
- If possible, how can I call  another lua script file?
- Which format (.lua?) must these multiple lua script files have?
-Do they have to be in the same directory as the calling lua script file?

Thanks for your answer!

Thomas Heidenreich