Again, you don't want to change regex, you want to create it in the first place. Maybe a simpler example, what if I wanted this in (pseudo-)C? with(s = fo

Again, you don't want to change regex, you want to create it in the first place. Maybe a simpler example, what if I wanted this in (pseudo-)C? with(s = fopen("/foo/bar", ...)) { ...; ...; println(readln(s)); ...; ...; } When the "with" clause ends, the file will automatically be closed. This is more or less bog standard RAII expressed as a new language construct. In Lisp, this is a feature you could build and provide as a library feature. In fact, we can do it, straight here in an HN comment. (defgeneric destroy (x) (:documentation "A destructor for use with the WITH feature".)) (defmacro with ((var = val) &body body) "Python-style RAII macro. VAR will be bound to the value of VAL, and upon exiting scope, will be destroyed with DESTROY." (assert (eq = ':=)) (let ((orig (gensym))) `(let* ((,orig ,val) (,var ,orig)) (unwind-protect (progn ,@body) (destroy ,orig)))) We can register a new destructor easily for open file streams: (defmethod destroy ((s stream)) (close stream)) (We could add some more error handling, etc. to make it more robust.) Now, we effectively have RAII in Lisp: (with (s := (open "/foo/bar" ...)) ... ... (write-line (read-line s)) ... ...) This is now real Lisp code you can actually run, completely integrated into the language, and nicely orthogonal to the existing gamut of features. This is a concept we can use almost immediately after learning about it, instead of waiting for Python's PEP 6363 to pass with consensus from people who may have different programming goals than you do.