This is a parameterless template intended for use on user language subcategories such as Category:User awa-1. It attempts to fill in the parameters of {{User language subcategory}} using the name of the category.
Usage edit
The template is intended to be all that's needed on a user language subcategory page and is used without parameters, thus :
It tests that is being used in category space, and that the category name is of the form "User iso-n", where "iso" is a valid ISO 639-1 or ISO 639-2 language code such as fr or nav, and "n" is the digits 1-5 or N indicating the level of proficiency at that language per Wikipedia:Babel. So for example it won't work on a programming language category like Category:User php-3. If the template fails one of these tests, it puts the page in Category:Errors reported by other category header templates.
The template uses Module:ISO 639 name to check the validity of the ISO code and to translate the ISO code into the name of the language, if this causes any problems complain over there!