Detecting the native locale

[Joshua Minor]

I'm trying to make Speak pick its default accent based on the native  
language of the laptop (per Walter's request http://dev.laptop.org/ticket/6656 
  )  This is a bit different from normal localization - although I  
need to do that also - because it is not just replacing strings.  My  
guess is that I can just look at the environment variable $LANG and  
pick an accent with a similar ISO 639 language code.

Can anyone confirm that using $LANG is appropriate for this?

Also, aside from just setting $LANG to something else, how can I test  
that this actually works?

-josh