In message <df1390cc04112810447ed53aa / mail.gmail.com>,
 `Simon Strandgaard <neoneye / gmail.com>' wrote:
> I have searched on google, but couldn't find any useful info on this.
> For instance I would like to rename urls from "show-all.html" to "show.cgi?all".

If the modified URL is allowed to be accessed directly,
redirection is easy to do it. 

require "webrick"

request_callback = Proc.new{|req, res|
  if %r{/show-all.html$} =~ req.path_info
    res.set_redirect(WEBrick::HTTPStatus::Found, "show.cgi?all")
  end
}

httpd = WEBrick::HTTPServer.new(
  :Port=>10080,
  :RequestCallback => request_callback,
  :DocumentRoot => Dir.pwd
)
trap(:INT){ httpd.shutdown }
httpd.start

-- 
gotoyuzo