I do have the my $class_name = ref($self) || $self; at the top of the function. The thing is that, after the first call to do_something() (which passes an object), I'm solely going to be passing in the class name of the parent. This means that I needed to be able to do a can() on a string, which you say I can.

Incidentally, the perldoc for UNIVERSAL::can() says that unless the first parameter is a bless'ed reference, it will return undef. I'm not doubting you, but the perldoc then is wrong. :(