gistfile1.txt

(defun perl-insert-package ()
  (interactive)
  (require 'perl-completion)
  (cond
   ((null buffer-file-truename) (error "no buffer-file-truename"))
   (t
    (let* ((s (replace-regexp-in-string
               (rx-to-string `(and bol ,(plcmp--get-lib-path) (? "/")))
               ""
               (expand-file-name buffer-file-truename)))
           (s (file-name-sans-extension (replace-regexp-in-string (rx "/") "::" (replace-regexp-in-string "^.+/lib/" "" s)))))
      (insert "package " s ";")))))