Richard wrote:
  I wonder if you could make a web server that used TECO
as the page
 processing language.  TECO could be used to process the headers and
 body of the request, modifying it in-place to produce the response
 headers and body. 
I can't imagine why not.  TECO is Turing-complete.  I wouldn't want the
job of writing it, though.  I've got less productive things to do with
my time.