I guess this is some kind of "class autovivification" you are doing?

Like I said, Perl's object system is very simple: ->isa('Error') (inherited from UNIVERSAL) is just looking up the inheritance tree, and the inheritance tree is defined by each package's @ISA, which is just an array of strings, so that's all I needed to define to make the "classes" "exist". perlmod is a good read on this topic.