title: redefining a single ruby method on a single instance with a lambda
body: <p>In Ruby, is there a way to redefine a method of a particular instance of a class using a proc?  For example:</p>
  
  <pre><code>class Foo
    def bar()
      return "hello"
    end
  end
  
  x = Foo.new
  y = Foo.new
  </code></pre>
  
  <p>(Something like):</p>
  
  <pre><code>y.method(:bar) = lambda { return "goodbye" }
  
  x.bar
  y.bar
  </code></pre>
  
  <p>Producing:</p>
  
  <pre><code>hello
  goodbye
  </code></pre>
  
  <p>Thanks.</p>