Include example of affecting fold direction in reduce

Author: zoffixznet

doc/Type/List.pod6

@@ -768,7 +768,13 @@ I<Note:> In the functional programming world, this operation is generally
 called a L<fold|
 https://en.wikipedia.org/wiki/Fold_%28higher-order_function%29#Folds_on_lists>.
 With a right-associative operator it is a right fold, otherwise (and usually)
-it is a left fold.
+it is a left fold:
+
+    sub infix:<foo>($a, $b) is assoc<right> { "($a, $b)" }
+    say [foo] 1, 2, 3, 4; # OUTPUT: «(1, (2, (3, 4)))␤»
+
+    sub infix:<bar>($a, $b) is assoc<left> { "($a, $b)" }
+    say [bar] 1, 2, 3, 4; # OUTPUT: «(((1, 2), 3), 4)␤»
 
 =head2 routine produce