.filter(|s| !["-", "+", "/", r"\"].contains(s))

                .filter(|s| !["-", "+", "/", r"\", ":"].contains(s))

    /// Quasimembership is defined for strings separated by `[-+/\]`

    /// Quasimembership is defined for strings separated by `[-+/\:]`

                    r"(\A|[-+/\\]){}(\z|[-+/\\])",

                    r"(\A|[-+/\\:]){}(\z|[-+/\\:])",