PEG tutorial example doesnt work

[Diego Antonio Rosario Palomino]

Hello, i am a new scheme user trying to exploit the peg library but have
encountered the following error :

guile c.scm
;;; note: source file /home/diego/Documents/Guile/c.scm
;;;       newer than compiled
/home/diego/.cache/guile/ccache/3.0-LE-8-4.6/home/diego/Documents/Guile/c.scm.go
;;; note: auto-compilation is enabled, set GUILEAUTO_COMPILE=0
;;;       or pass the --no-auto-compile argument to disable.
;;; compiling /home/diego/Documents/Guile/c.scm
;;; /home/diego/Documents/Guile/c.scm:20:57: warning: possibly unbound
variable `⇒'
;;; compiled
/home/diego/.cache/guile/ccache/3.0-LE-8-4.6/home/diego/Documents/Guile/c.scm.go
Backtrace:
In ice-9/boot-9.scm:
  1752:10  6 (with-exception-handler   #:unwind?  # )
In unknown file:
           5 (apply-smob/0 #<thunk 7fcf881b52a0>)
In ice-9/boot-9.scm:
    724:2  4 (call-with-prompt   #<procedure default-prompt-handle…>)
In ice-9/eval.scm:
    619:8  3 ( #(#(#<directory (guile-user) 7fcf881b9c80>)))
In ice-9/boot-9.scm:
   2836:4  2 (save-module-excursion )
  4388:12  1 ()
In /home/diego/Documents/Guile/c.scm:
    20:57  0 (_)

/home/diego/Documents/Guile/c.scm:20:57: Unbound variable: ⇒

c.scm
Description: Binary data