I've toyed a little bit with the idea of a grep(/addition to the RE engine) for XML, which can take flags like this word should be part of an attribute name, return the element name.

Some kind of diff would be a (hrm..) simple extension of the idea.

I didn't think it would be that interesting, but here it would find a use. (-: I have a too big hobby module already, anyway. :-)

Update: What I meant was, a grep thing which understood XML syntax and e.g. allow one grep pattern over the value of an attribute and another grep pattern over the CDATA for that same element.

I don't really know what would be useful (I don't really need it for what I am thinking of doing) and I doesn't have time now anyway.