class_sinatra.rb

#Classy Sinatra
#Launch with ruby app.rb
require 'rubygems'
require 'sinatra/base'

#module MyModule
  class MyApp < Sinatra::Base
    #set :raise_errors, Proc.new { false }
    #set :sessions, false
    #set :static, true
    #set :show_exceptions, false 
    #set :public, "public"

      get '/' do
        "Hello World!"
      end
   end
#end

#The missing part of the puzzle
MyApp.run!

classic_sinatra.rb

#Classic Sinatra
#Launch with ruby app.rb

require 'rubygems'
require 'sinatra'

get '/' do
   "Hello World!"
end