Is it possible to change the definition of '~' from that of a destructor/finalizer and into that of an underscore '_' ?

Right, in addition to the destructor it's also the unary bitwise not / complement operator. So no, it's definitely not possible. I just wonder for what kind of "demarcating" one would use the ~ character instead of _. They actually look quite similar and can easily be mistaken. So it would counteract the actual goal. What kind of variables do you want to demarcate ? Just give them meaningful names. The only things you may want to distinguish are private vs public variables. I generally use the "old" m_VarName style for private member variables. Method arguments I almost always prefix with an "a" (for argument).