anchor.diff:            ,value)
          `(lookup-with-default ,getter ,key-sym ,default-sym)))))
   
  -(defun env (key &optional (default +env-default+))
  +(defun env (key &optional (default *env-default*))
     "Look up the given variable in the current environment."
     (multiple-value-bind (entry found) (fset:lookup *environment* key)
       (if found
  
positive.code:   (:documentation
     "Everything there is to know about an environment variable."))
  
  (define-once-global +env-default-binding+ (make-instance 'environment-binding)
    (:documentation
     "The default state for an environment binding."))
  
  (defun deconstruct-environment-binding (binding)
    "Parse a string describing an environment binding.
  
negative.code: (defun environment-to-map ()
    "Translate the posix environment of the current process into a map
  suitable for storing in `*environment*'."
    (let ((map (fset:empty-map *env-default-binding*)))
      (do-iterator (binding (environment-iterator))
        (multiple-value-bind (key value) (deconstruct-environment-binding binding)
          (setf map (fset:with map key (make-instance 'environment-binding
  