SPACK is a toy package system for LISP.

spack.lisp

;;
;; # SPACK
;;
;; SPACK is a toy package system for LISP.
;;
;; ## Syntax
;;
;; Predefined functions and variables are unprefixed.
;; User-defined functions and variables are prefixed by package
;; declared by `spack/defpackage'. There is a separator `/' between
;; the package and symbol name. `~' is an alias for current package.
;; You can import external symbols into the current package by
;; `spack/import', which takes a package and symbols as arguments.
;;

(defparameter spack/*package* 'spack)

(defmacro spack/defpackage (package)
  `(defparameter spack/*package* ',package))

(defun spack/resolve (stream char)
  (declare (ignore char))
  (read-char stream t nil t)
  (let ((sym (read stream t nil t)))
    (intern (format nil "~a/~a" spack/*package* sym))))

(set-macro-character #\~ #'spack/resolve)

(defmacro spack/import-functions (package &rest symbols)
  (when symbols
    `(progn
       (setf (fdefinition ',(intern (format nil "~a/~a" spack/*package* (car symbols))))
             #',(intern (format nil "~a/~a" package (car symbols))))
       (spack/import ,package ,@(cdr symbols)))))

;;
;; Example
;;

(spack/defpackage example-lib)
(defvar ~/pi 3.141592)
(defun ~/sayhello ()
  (print ~/pi))

(spack/defpackage example-main)
(spack/import-functions example-lib sayhello)
(~/sayhello)