with_return --> ro and writer for the songle setting case
destroyed_session --> ro + writer + use predicate for checking
path_info --> ro + writer
vars --> 'ro'

vars is a hash ref which lives in the request, being 'ro'
doesn't blocked it from being written to, but the attribute itself
shouldn't be assigned to (hash isn't replaced).
cookies --> 'ro'

cookies is a hash ref which lives in the request, being 'ro'
doesn't blocked it from being written to, but the attribute itself
shouldn't be assigned to (hash isn't replaced).