If it works, but not quite the way you wanted it to, that's a bug (in the mind of the programmer, anyway).

Well, if it's not documented to work the programmer can't really expect anything from it. I don't see how that can be considered a bug if you can't expect it to work in any way at all.

And if you want to allow for $instance->new(), you'll have to painstakingly document whether this creates a new "empty" object, or whether it creates a copy of the instance it was called on.

How painstakingly is "Doing $obj->new is the same as doing ref($obj)->new"?

-Anomo