gistfile1.rb

module Awesome
  def baz
    puts "baz"
  end
end

class Foo
  
end

backup_foo = Foo.clone

class Foo
  include Awesome
end

foo_obj = Foo.new
foo_obj.baz # => baz

Object.send :remove_const, :Foo

Foo = backup_foo

foo_obj.baz # => baz
Foo.new.baz # NoMethodError: undefined method ‘baz’ for #<Foo:0x1d650>