eg)
For a module developper who maintains "mod_a" in mainly Spanish :
$ xoops_lang_check.php module/mod_a spanish english
This command shows you which constant definitions of english are insufficient.

$ xoops_lang_check.php --patch module/mod_a spanish
This command append constant definitions into apropriate files for all languages automatically.

For a translator who maintain "mod_a" from english to French :
$ xoops_lang_check.php --patch module/mod_a english french
After this command, you can easily found and edit the constants added new.

This tool is written in PHP CLI. Even if you don't have PHP CLI, converting to another type of PHP is easy, I think.