My main concern is res.headers['Set-Cookie'] could become nil when there's actually no cookie.  If that condition occurs, the code is basically like:

	nil.split(',') || ''

And you ned up getting:

	NoMethodError: undefined method `split' for nil:NilClass

We probably have plenty of module that write res.headers['Set-Cookie'].split.  But in my opinion we should handle return values more carefully.