eval

   1  #!/usr/local/bin/ruby
   2  # encoding: utf-8
   3  class Array
   4    def yield
   5      yield self
   6    end
   7    def ival(s)
   8      self.send(s)
   9    end
  10  end
  11  
  12  [1,2,3].yield do |s|
  13    puts  s.reverse!
  14  end
  15  
  16  [1,2,3].instance_eval do
  17    puts self.reverse!
  18  end
  19  
  20  a = [1,2,3]
  21  a.ival "reverse!"
  22  p a