How to export associative arrays to an embedded lua script?

["linuxfan@..." <linuxfan@...>]

Hi list,

I'm embedding Lua in a pascal program which uses several 
tables filled with key/values pairs,
for example

  xGuiPrefs['lang']  :
= 'en';

or

  xEnviron['screenwidth'] := 480;

...and so on. Now I 
want to expose those tables (about 8 or 9) to Lua, so a script can read 
and write values to them. I started with:

  luaL_newmetatable(L, 
'xplcmetatable');
  lua_pushstring(L, '__index');
  lua_pushcfunction
(L, xl_getxtable);	// my routine to read values
  lua_rawset(L, -3);
  
// (__newindex is left out, for the moment)

to create a metatable 
which will be associated to the various tables I will export.
Then for 
every table to export I do this:

  lua_newtable(L);
  luaL_setmetatable
(L, 'xplcmetatable');
  lua_setglobal(L, 'env');

This creates a Lua 
table named "env". If a script tries to read a value from table env:

  
print (env.screenwidth)

lua nicely calls my routine xl_getxtable() 
with two arguments - the table and the key.
My problem is that I don't 
know how to get the table name lua refers to; while the key is passed 
as a string, the table is passed as a lua internal variable which means 
nothing to me. I tried to search around in examples, docs, and so on, 
but with no success. I only discovered the Registry where, may be, I 
can store the table as key and its name as value, so I can later fetch 
the name of the table. Probably I will end up using different 
xl_getxtable() functions, each one with its hard-coded table name 
inside; it would be faster and the tables to export are not so many. 
But while am at it, I want to understand.

Regards,
Linuxfan