Common Lisp (packages and symbols are first class). There are some gotchas at first but then they feel quite natural. You write your code in one place and manag

Common Lisp (packages and symbols are first class). There are some gotchas at first but then they feel quite natural. You write your code in one place and manage visibility elsewhere. This allows for example to make a symbol exported in different packages, or take separate code and provide a unified facade package. But most of the time you just need to define the public interface of your code and this is quite easy.