As far as I am aware, the only way to do this is to have the called-class (explicitly) invoke its superclass.   (Or, in the case at bar, both the Berlin and the Paris methods would have to explicitly call msg(), and if there were more than half-a-dozen of these I’d be declaring another class.)

As far as I am aware, the (“unadorned” ...) Perl language does not provide for any sort of “implicit wrappers.”