ACT-R Lisp dynamically create chunk

(defun creer-bagage (=poids =categorie)
  (let* ((timestamp (get-universal-time))
         (=id (format nil "~8d" (mod timestamp 100000000)))
         (=dimensions 
           (case =categorie
             (1 (list 3 3))  ;; Example dimensions for category 1
             (2 (list 6 2))  ;; Example dimensions for category 2
             (3 (list 6 3))  ;; Example dimensions for category 3
             (otherwise (error "Catégorie invalide : ~a" =categorie)))))
    
    ;; Création du chunk en mémoire déclarative
    )

    (add-dm (isa baggage
                 id =id
                 categorie =categorie
                 poids =poids
                 dimensions =dimensions
                 position nil
                 est-place nil))
                 
               ;   (define-chunks-fct (("new chunk") isa bagage id =id))
                 )

When running this code with parameters say 1 and 1 I have this as result:

BAGGAGE0
   ID  =ID
   CATEGORIE  =CATEGORIE
   POIDS  =POIDS
   DIMENSIONS  =DIMENSIONS

So it does not pass the variables but instead treats them as strings. Please how do i fix it. Thanks