; (let-alist): Document double-dot escape syntax. (Bug#75852)

lisp/emacs-lisp/let-alist.el

@@ -141,6 +141,12 @@ the variables of the outer one.  You can, however, access alists
 inside the original alist by using dots inside the symbol, as
 displayed in the example above.
 
+To refer to a non-`let-alist' variable starting with a dot in BODY, use
+two dots instead of one.  For example, in the following form `..foo'
+refers to the variable `.foo' bound outside of the `let-alist':
+
+    (let ((.foo 42)) (let-alist \\='((foo . nil)) ..foo))
+
 Note that there is no way to differentiate the case where a key
 is missing from when it is present, but its value is nil.  Thus,
 the following form evaluates to nil: