I don't think global variables were mentioned in the article. Do you mean the global (top-level) namespace? If so, then yeah, "Don't do that" is pretty much the solution.
Sorry, maybe this isn't correct Ruby nomenclature, but I see Array simply as a global object, which can be modified, with rather obvious consequences. It's sad that I feel old enough to say this, but isn't this a problem that we solved a long time ago?
"Don't do that" is one solution, Alan Kay's idea of "worlds" is another.