diff --git a/emacs/init.org b/emacs/init.org
index 799b9e0..4ef872f 100755
--- a/emacs/init.org
+++ b/emacs/init.org
@@ -321,6 +321,30 @@ Running a shell command as sudo:
       (shell-command command)))
 #+END_SRC
 
+** Buffer switch hooks
+I want to be able to run code whenever I switch to a buffer running certain modes. The code to run is stored in a alist mapping mode names to lists of code to run (stored as a raw data structure to be eval'ed):
+#+BEGIN_SRC emacs-lisp
+  (defvar buffer-mode-hooks '())
+#+END_SRC
+
+To add a new hook, push the code to run onto the correct list:
+#+BEGIN_SRC emacs-lisp
+  (defun add-buffer-mode-hook (mode fn)
+    (if-let ((existing-entry (assoc mode buffer-mode-hooks)))
+	(push fn (cdr existing-entry))
+      (let ((new-entry `(,mode . (,fn))))
+	(push new-entry buffer-mode-hooks))))
+#+END_SRC
+
+Whenever the buffer changes, look up the major-mode to see if there is any code to run:
+#+BEGIN_SRC emacs-lisp
+  (defun run-buffer-mode-hooks ()
+    (when-let ((entry (assoc major-mode buffer-mode-hooks)))
+      (dolist (fn (cdr entry))
+	(funcall fn))))
+
+  (add-hook 'buffer-list-update-hook #'run-buffer-mode-hooks)
+#+END_SRC
 * Customization File
 I don't want anything to write to my init.el, so save customizations in a separate file:
 #+BEGIN_SRC emacs-lisp