### Example:

  ```ruby
  # example.rb
  e = [1]
  def e.rewind; p :r end
  c = e.chain(e)
  c.each{break c}.rewind
  ```

#### Before this patch:

  ```terminal
  $ bin/mruby example.rb
  :r
  :r
  ```

#### After this patch (same as Ruby):

  ```terminal
  $ bin/mruby example.rb
  :r
  ```