Rephrase sentence and add small example

doc/Language/functions.pod6

@@ -177,14 +177,15 @@ one to skip commas between named arguments.
 =head2 Return values
 
 Any C<Block> or C<Routine> will provide the value of its last expression as a return value
-to the caller. If L<return|/language/control#return> or
-L<return-rw|/language/control#return-rw> are called their parameter, if any,
+to the caller. If either L<return|/language/control#return> or
+L<return-rw|/language/control#return-rw> is called, then its parameter, if any,
 will become the return value. The default return value is L<Nil|/type/Nil>.
 
     sub a { 42 };
     sub b { say a };
-    b;
-    # OUTPUT: «42␤»
+    sub c { };
+    b;     # OUTPUT: «42␤»
+    say c; # OUTPUT: «Nil␤»
 
 Multiple return values are returned as a list or by creating a
 L<Capture|/type/Capture>. Destructuring can be used to untangle multiple return