How to tell if this is the top-level script?

[Geoff Leyland <geoff_leyland@...>]

Hi,

For a while I've been writing my Lua modules like this:

if ... then module(...) end

and at the end of the module:

if not ... then
  -- do some tests or something suitable when called as a top-level  
script
end

Which worked really nicely - I could use the code as a module, or get  
it to run its self-tests without fuss.

However, it's stopped working, possibly since I upgraded to 5.1.2 or  
since I started using LuaBinaries - the error is on the "if not ...  
then" line, and says "cannot use '...' outside a vararg function".

Does anyone have any suggestions as to how to achieve the same thing  
(work out if we're being run as someone else's module or as a top- 
level script) a better way?

Thanks in advance,
Geoff