module-testing.rb

class Foo
  include Module.new {
    def this_works
    end
  }

  include Module.new do
    def this_doesnt_work
    end
  end
end

foo = Foo.new
foo.this_works
foo.this_doesnt_work

The second example is parsed like this:

include(Module.new) do
  def this_doesnt_work
  end
end

That is, the block is an argument to include, not to Module.new.

It's failing because the block precedence is being applied wrongly in the first. The block is being consumed by include in one case and Module.new in the other.

https://gist.github.com/3881661