gistfile1.rb

require 'sinatra'

module Sinatra
  module Foo
    module Helpers
      def foo
        @bar = 'Bye'
      end
    end
    def self.registered(app)
      app.helpers Helpers
      app.set :foo, "bar"
      
      app.get "/foo" do
        erb :bar
      end
    end
  end
  register Foo
end

get '/hi' do
  @bar = 'Hello'
  foo
  @bar
end