CL-WHO is a Lisp markup language which provides convenient means to convert S-expressions intermingled with code into (X)HTML, XML. It tries to create efficient code in that it makes constant strings as long as possible. In other words, the code generated by the CL-WHO macros will usually be a sequence of WRITE-STRING forms for constant parts of the output interspersed with arbitrary code inserted by the user of the macro. CL-WHO will make sure that there aren't two adjacent WRITE-STRING forms with constant strings.

http://weitz.de/cl-who/