Class::Std 0.0.8 should now "just work" with mod_perl. From the docs:
This subroutine sets up all the infrastructure to support your
Class::Std- based class. It is usually called automatically in a
"CHECK" block, or (if the "CHECK" block fails to run -- under
"mod_perl" or "require Class::Std" or "eval "..."") during the
first constructor call made to a Class::Std-based object.
In rare circumstances, you may need to call this subroutine
directly yourself. Specifically, if you set up cumulative,
restricted, private, or automethodical class methods (see below),
and call any of them before you create any objects, then you need
to call "Class::Std::initialize()" first.
So you shouldn't need to call the new subroutine yourself in most cases.