Yes, I guess the single-quote part was a bit of a slip-up on my part. There is no reason for the desired effect that I am looking for to be acheived exclusively with single-quotes. As a matter of fact, double-quotes would be even better since they represent (and do) interpolate.
My mess-up was based on the fact that I wanted a string to be re-assigned when it doesn't do it automatically. The single-quote part was my goof, and a bit of an exageration. Now I can't find any good reason why they couldn't be double in the first place. Thanks for pointing that out. Its important.