using a module added by gahr on Mon Feb 25 16:02:10 2019

%%% in foo.scm
(define-library (foo)
  (export foo)
  (import (scheme base))
  (begin
    (define (foo n) (+ n 3))))

%%% in main.scm
(import
  (scheme base)
  foo)

(display (foo 5))
(display "\n")