app.rb

# -*- coding: utf-8 -*-
require 'sinatra'

module MyCustomRequestMethod
  def hey(path,opts={},&blk)
    route __method__.to_s.upcase,path,opts,&blk
  end
end

module Sinatra
  register MyCustomRequestMethod
end

script = <<SCRT
def upcase(str)
  str.upcase.split(//).reverse.join('')
end
SCRT

## ex. curl -X HEY "http://localhost:4567" -d "text=abcdefghijk"
hey '/' do
  puts "request.env[\"REQUEST_METHOD\"] is `#{request.env["REQUEST_METHOD"]}`, params is "+params.inspect
  eval(script).__send__ :upcase, params[:text]
end

get '/' do
  script
end