It was initially a fork of uri-template but has been mostly rewritten from scratch. Most notably implementation of operators has been added. The missing operators in uri-templates rendered it mostly useful for destructuring URIs.
Some effort has been put in testing cl-uri-templates at least on SBCL. Please report any test failing in test.lisp.
Author: Thomas de Grivel
Source repository: https://github.com/thodg/cl-uri-templates