anchor.diff:  (defparameter +log-level-from-string+ 
     '("OFF" "FATAL" "ERROR" "WARN" "INFO"
       "DEBUG" "USER1" "USER2" "USER3" "USER4" "TRACE"
  -    "USER5" "USER6" "USER7" "USER8" "USER9"))
  +    "USER5" "USER6" "USER7" "USER8" "USER9" "UNSET"))
   
   
   (defun make-log-level (arg)
  
positive.code:     (values)))
  
  
  (defun set-log-level (logger level)
    (declare (type logger logger))
    (let ((level (make-log-level level)))
      (declare (type fixnum level))
      (setf (logger-app-data-level (current-appdata logger))
            (when (/= level +log-level-unset+) level))
      (adjust-logger logger)
      (values)))
  
  (defun add-appender (logger appender)
    (declare (type logger logger) (type appender appender))
  
negative.code:                (error "~s does not match any log levels" arg))))
          ((and (numberp arg)
                (>= arg +min-log-level+)
                (<= arg +log-level-unset+))
           arg)
          (t (error "~s does not match any log levels" arg))))
  
  