anchor.diff:             #:algebraic-match-with
              #:algebraic-guard
              #:enable-match-syntax
  +           #:disable-match-syntax
              :left-bracket
              :right-bracket
              :*readtables-stack*))
  
positive.code:  amatch arg &body clauses
   Same as MATCH, except that handling of algebraic types is enabled"
    (if (not (boundp 'abacus-typespec))
      (defvar abacus-typespec nil))
    `(let  ((abacus-it nil))
       (match ,arg ,@clauses)))
  
  
negative.code: 
  (defvar *readtables-stack* nil)
  
  (defconstant left-bracket #\|)
  (defconstant right-bracket #\])
  
  (defmacro enable-match-syntax ()
  