On the one hand, you're right, a concatination operator is redundant, given interpolation. On the other hand, TMTOWTDI.

Somtimes, I just don't want to have to write somthing in terms of interpolation instead of concatination, even if they are properly the same thing. (They are, in fact, completly the same thing.)

So my vote is still for ~ being the concat operator. Which is good, because the thread on perl6-language is good and dead, which is what I suggest this thread becomes. This is one of those things that could easily be argued about until the end of time -- almost every possible view has good things and bad things going for it.