Well, actually, no it does not differ.  The ARG instruction deals with just strings, which are immutable.  If all you are passing are string values, then there is no way to alter the value of the string object such that the change would be visible from both variable values.  This is true whether you are using ARG or USE ARG.  It is only because you are using array objects, which do have mutable internal state can you see the changes. 

Well, there you go, always something new to learn. What you say makes sense, Rick, I didn't think about that strings are immutable.

Getting there, but slowly ;)