In retrospective, I shouldn't have brought up || as I don't see any use for an lvalue expression X || Y neither, which would be equivalent to the "Elvis operator".

A possible novelty could be a binary operator that:

• acts like defined(X) ? X : Y
• yields an lvalue, provided X and Y are lvalues
• evaluates X only once

If X // Y was an lvalue, it would satisfy these criteria. As it currently isn't, it could hardly break anything as such usage doesn't compile. No new operator, just an extension. In a Perlish sense: One more way to do it.