[eluser]xwero[/eluser]
It doesn't makes much sense that the auto loaded files don't change if you change the language then what is the point of having different directories?
so following the user guide you would have to have en_app_lang.php and br-pt_app_lang.php in both directories?
With the lang->load method it should be possible to overwrite the autoloaded stings but that doesn't work either.
It seems like the autoloading of languages files could need some more work.