sub get_translation_dir
{
  my $lang = shift;

  # have we encountered this before?
  return $vars{"translation_dir_$lang"} if $vars{"translation_dir_$lang"};

  # I think languages are sent as semicolon-seperated values, e.g.
  # en;en-US for someone who only speaks English ... or 
  # fr;fr-FR;en-FR;en for someone who prefers French, but will accept English.
  # modify if that's wrong.
  my @choices = split /;/, $lang;

  for (@choices)
  {
    # have we seen this one before?
    return $vars{"translation_dir_$lang"} = $vars{"translation_dir_$_"} if $vars{"translation_dir_$_"};

    # no?  Do we have such a translation?
    if ( -d "$vars{root_dir}/$_" )
    {
      # save it to the cache, and return.
      return $vars{"translation_dir_$lang"} = $vars{"translation_dir_$_"} = "$vars{root_dir}/$_";
    }
  }
  # if we get this far, try no language.
  return get_translation_dir('');
}