Requirements

… for the language in which Krextor is implemented:

Language	XML support	DocumentTraversal	PatternMatching (XML)	FunctionalProgramming
XSLT	built in	default behaviour	excellent (XPath)	possible but hackish (FXSL)
XQuery		manual recursion		processor extension
Scala	scala.xml		fair	excellent
JavaScript	DOM, E4X		must call XPath	possible
Scheme	SXML	pre-post-order macro	XPath, various Scheme constructs	excellent
Haskell	HXT	XML arrows	XPath, convenience functions	excellent
CDuce	built in	manual recursion?	XPath-like (downwards)	excellent

See also  this blog post and its comment for a discussion.