(defun test-foo ()
  (eval `(defpackage :package-local-nicknames-test-1
           (:use)
           (:local-nicknames (:l :cl))))
  (let* ((*package* (find-package :package-local-nicknames-test-1))
         (cons0 (read-from-string "L:CONS")))
    (prin1-to-string cons0)))
      
CL-USER> (test-foo)
"L:CONS" ;; SBCL
"CONS"   ;; ECL