For tree-oriented pattern matching syntax, I'd recommend for inspiration the RELAX NG Compact Syntax, rather than XPath. Technically, RELAX NG is an XML schema validation language; but the basic principle that it uses is to describe a tree-oriented pattern, and to consider the document to be valid if it matches the pattern.
XPath, by contrast, isn't so much about pattern matching as it is about creating a tree-oriented addressing scheme. Also note that S05 includes an option near the end about matching elements of a list rather than characters of a string; IMHO, a robust "structured data"-oriented pattern-matching technology for perl6 ought to use that as a starting point. -- Jonathan "Dataweaver" Lang
