Concrete XML syntax is used in the Haskell Server Pages extension 
language, and a description can be found in the paper "Haskell Server 
Pages through Dynamic Loading" by Niklas Broberg, published in Haskell 
Workshop '05.

Regular expression pattern matching is described in the paper "Regular 
Expression Patterns" by Niklas Broberg, Andreas Farre and Josef 
Svenningsson, published in ICFP '04.