An XML-based functional programming language?

Is there an XML-based (probably functional) programming language?

I want to make something like TeX but in XML format. TeX macroses are 
Turing complete. I want to do a similar thing in XML. That is I want to 
define macroses in XML and moreover do Turing complete computations in XML.

Note that currently I need only the programming capabilities, not 
something more (not text formatting, for instance).

Any partial realization of my request (for instance, macroses but not 
Turing complete) are of interest.