*{; no strict 'refs'; \*{ "${pkg}::type" } } = sub () { $type };
push @{; no strict 'refs'; \@{ "${pkg}::ISA" } }, __PACKAGE__;
# ... and so on

I really don’t feel like I have anything to add but I suppose it may not be obvious that the point of this exercise is to surgically limit the lifting of the refs stricture to just the desired symbolic dereference (without leaking it even as far as any other part of the expression) – in the most compact form possible.

I also suppose I ought to expand on it by way of explanation for the less travelled in the dustier corners of Perl 5 syntax: