doc: adjust package messages; add more sample code

doc/sample/Expressions.im

@@ -142,7 +142,7 @@ pkg = { { 0 }, { 1 }, { y for y in huh } }.
 pkg = { x multiplyBy:2 for x in wow if x > 2 }.
 
 pkg->x = 32.
-K = (1 multiplyBy:2, 4).
+k = (1 multiplyBy:2, 4).
 
 for (x, y) in pkg do
 	cout put:'{x}: {y}'
@@ -153,8 +153,22 @@ pkg[0] = 16.
 /* All of these accesses are equivalent */
 pkg['x'] = 32.
 pkg->x = 32.
-pkg put:32 at:'x'.
+pkg at:'x' put:32.
+
+v = pkg['x'].
+v = pkg->x.
+v = pkg at:'x'.
+
+pkg2 = {
+    onEnter => [
+        cout put:'start!'
+    ],
+
+    onExit => [
+        cout put:'end!'
+    ]
+}.
 
 index = 'x'.
 pkg[index] = 32.
-pkg put:32 at:index.
+pkg at:index put:32.