Currently (Prime 5) search and replace can be used to find partial-word matches, but replace insists on making full-word replacement for variable names. Search-and-replace completely destroys string values.
In other words, if I have variables named "MyApple" and "MyOrange", and I want to change "My" to "Your", I have to do this by hand. Search-and-replace "My"->"Your" ends up with two variables named "Your" and "Your" which is not helpful.
Search-and-replace does currently work as expected in text regions, but not for variable names, and certainly not for string values.