guile-examples/modules/subdir/mention.scm

;; IMPORTANT!
;; If the module is defined in a subdirectory, the subdirectory must be
;; mentioned as in this example and the names must be equal to the subdirectory
;; name and the file name of the file, which defines the module.
(define-module (subdir mention))

(define-public mention-bertified
  (λ (name)
    (display (string-append name "bert"))))