How to use module()

["Jeff Sheets" <jeff.sheets@...>]

Though I see in the manual what the module function does, I'm wondering 
how one uses it properly.

I am assuming it is intended to be used at the beginning of a module lua 
file, which is intended to be required into another lua file.  Am I 
correct?

Also, when are the functions given as extra parameters to module() 
executed, and what environment do they have before execution?