Confusion over passing by reference vs passing by value

[hanness]

This is expected as strings are *always* passed by offsets.  The solution is as you have found -- assign to a temp variable and don't modify the original. 

Ah, very good. I wasn't aware that there was a difference between how the strings and numerical variables were handled in this regard.

I learn new things every day. The trick is in trying to remember all of it :-)