anchor.diff:  
   (defun set-walk-through-value (name values)
     "Set value of variable of type walk-through. Keep list of value and index in symbol's plist."
  +;  (script-debug "set-walk-through-value ~A ~A~%" name (eval-if-needed values))
     (setf (get name 'values) (eval-if-needed values))
     (setf (get name 'index) -1)
     (setf (symbol-value name) 'value-not-set-before-first-call-to-next-step-§->!))
  
positive.code:   (funcall *generate* (template 'nothing)))
  (export 'real-next-walk)
  
  (defun set-walk-through-value-in-multiple (name val symbols values)
    (setf (get name 'values) values)
    (setf (get name 'symbols) symbols)
    (setf (get name 'index) -1)
  
negative.code:   (let ((values (eval-if-needed listval)))
      (loop 
         for sym in listsym
         do (set-walk-through-value-in-multiple sym listsym values))))
  
  (defun eval-a-variable (var val)
    "Parse variable definition and set it (or them)." 
  