prepend_prepend.rb

Module.new do
  def prepend(m=nil, &blk)
    if block_given?
      super(Module.new(&blk))
    else
      super
    end
  end
end.tap { |pre| Module.prepend pre }

class Foo
  def bar
    puts "class"
  end
end


Foo.prepend do
  def bar
    puts "prepended"
    super
  end
end

module Bar
  def bar
    puts "module"
    super
  end
end

Foo.prepend Bar

Foo.new.bar # => module
            #    prepended
            #    class

There's no need to explicitly pass arguments to super on line 6. Just calling super with no parens passes all original arguments by default because Ruby is all about consistency.

Edit: Sorry, I meant line 6.

@rwz Fixed.