[xsl] string manipulation language based on xslt?

Hey
I seem to remember encountering an xml language, based on xslt (by saying based
i mean that it had constructs with some of the same names) which used grammars
for matching text inputs. anyone know the language i'm talking about, i'm
writing some stuff and it will make a good referenced/addendum. note, I am not
thinking of txl (this was definitely an xml language i remember, and it was
discussed as using xslt constructs). 

-- 
Bryan Rasmussen