`*stack*` is a dynamic variable in `clojure.xml`. It is publicly accessible but is an implementation detail, not an API intended for public use. section 23.21
Its value and role in XML processing are not specified. Despite the name, it should not be confused with a last-in, first-out stack built from a list or vector using `conj`, `peek`, and `pop`. section 23.21 section 9.4.1 section 12.6
