Kill and copy an expression result.

kill-and-copy-expression-result.el

(define-key global-map (kbd "C-x C-j")
  (defun kill-copy-eval-sexp (arg)
    "The function `kill-copy-eval-sexp' kill-saves and copies an
expression result using `simpleclip-mode'."
    (interactive "P")
    (set-register ?1 (format "%s"(eval-last-sexp arg)))
    (simpleclip-set-contents (get-register ?1))
    (kill-new (get-register ?1))
    ))