File scope method

lib.rb

class OpenClass
  module InternalMethods
    refine OpenClass do
      def foo
        :foo
      end
    end
  end
  using InternalMethods
  def bar
    foo
  end
end
p OpenClass.new.bar

module InternalMethods
  refine Object do
    def one
      1
    end
  end
end
using InternalMethods
p one

main.rb

#! /usr/bin/env ruby

require './lib'

class OpenClass
  def baz
    foo
  end
end

OpenClass.new.baz rescue puts "error: OpenClass#baz cannot call"
one rescue puts "error: `one' cannot call"

# $ ruby main.rb
# :foo
# 1
# error: OpenClass#baz cannot call
# error: `one' cannot call