Exploring the meaning of Ruby 1.9 respond_to_missing?

respond_to_missing?

class Foo
  def respond_to?(sym)
    if sym == :foo
      return true
    else
      super
    end
  end
end
class Bar
  def respond_to_missing?(sym, p)
    if sym == :foo
      return true
    else
      super
    end
  end
end

[Foo, Bar].each do |klass|
  [[:respond_to?, :foo], 
   [:respond_to_missing?, :foo, false], 
   [:method, :foo]].each do |method, *args|
    r = begin
      klass.new.send(method, *args)
    rescue => ex
      ex
    end
    puts "Calling #{klass}##{method.inspect}(#{args.join(', ')}) # => #{r.inspect}"
  end
end