XbindKey guile config for volume controls with extra mouse button (button 8, normally 'back')

.xbindkeysrc.scm

;; This configuration is guile based.
;; https://www.gnu.org/software/guile/learn/
;; Based on the awesome script created by Zero Angel:
;; https://www.linuxquestions.org/questions/linux-desktop-74/%5Bxbindkeys%5D-advanced-mouse-binds-4175428297/

;; We'll need a named pipe later, because we can't share FDs
(if (not (file-exists?  ".xbindkey.pipe"))
    (run-command "mkfifo .xbindkey.pipe")
    (sleep 1)
)
;; In case we want to force the file type:
;; (if (not (eq? (stat:type (stat ".xbindkey.pipe")) 'fifo)) (exit 1))

;; Run xte to execute key presses
(run-command "xte <.xbindkey.pipe")

;; Action

(define fo (open-file ".xbindkey.pipe" "w0"))
(define has_scrolled 0)

;; Extra mouse button
(xbindkey-function '("b:8") (lambda ()
    ;; This seems to be needed to avoid duplicate calls after a single press
    (remove-all-keys)
    ;; Scroll Up
    (xbindkey-function '("b:4") (lambda ()
        (display "key XF86AudioRaiseVolume\n" fo)
        (set! has_scrolled 1)
    ))
    ;; Scroll Down
    (xbindkey-function '("b:5") (lambda ()
        (display "key XF86AudioLowerVolume\n" fo)
        (set! has_scrolled 1)
    ))
    ;; Released
    (xbindkey-function '(release "b:8") (lambda ()
        (if (= has_scrolled 0) (display "key XF86AudioMute\n" fo))
        (set! has_scrolled 0)
    ))
))