zuc.rb

def path matcher
  lambda {|req|
    return unless match = req.env["PATH_INFO"].match(/^\/(#{matcher})(\/|$)/)

    path = match.captures[0]

    req.env["SCRIPT_NAME"] += "/#{path}"
    req.env["PATH_INFO"] = "/#{match.post_match}"
  }
end

app = lambda {|env|
  req = Rack::Request.new(env)
  res = Rack::Response.new

  case req
  when path("users") then
    case req
    when path("all") then
      res.write "here they are"
    else
      res.write "users"
    end
  when path("about") then
    res.write "about"
  else
    res.write "fail"
  end

  res.status = 200
  res.finish
}

run app