Lambda the Ultimate

With XQuery 3.0 support of first class functions and a whole host of other fp goodness

http://www.w3.org/TR/xquery-30/

be interested in comment here if 3.0 is missing anything.

Having a small fp language work on declarative markup (as well as json, text, etc) is a powerful idiom.

I am sure I am demonstrating ignorance, but I am not aware of a similar(dynamic, typed) programming language that embodies fp principles so concisely.