[Screencast] Elixir: Object Orientation and charming syntax on top of Erlang

2) Yes, adding a syntax to easily change instance variable values is one of the most asked features. The tricky part is, we cannot do the following:

    @foo = "bar"

I was thinking about something like @{'foo : "bar"}, but I haven't decided yet. Suggestions are welcome. :D

I still haven't decided if Elixir will have open class or if I will add refinements or classboxes.

On other hand, module_eval is what allows frameworks like Rails to dynamically add code to a class, so you can do stuff like:

    class Post
      has_many :comments
    end

This isn't monkey patching. Ruby's classes are open (they can be modified on the fly), so you can monkey patch modules with new functionality. In a language like C, if you wanted to extend a library, you might modify it and recompile.

Ruby's module_eval and class_eval are meta-programming tools that let you programmatically add methods to classes (and lots of other stuff), this can be combined with monkey patching, if you so desire.