Tricky subclassing problem: Parent class method uses static value from child class

[don.hosek]

I want to be able to do something along the lines of:

package A;
@ISA = ('B');
use Class::Std;

my $foo='this';

package C;
@ISA = ('B');
use Class::Std;

my $foo='this';

package B;
use Class::Std;

sub method {
do something with $foo
}

(obviously, there's a bit more to this, but I'm trying to abstract
things as much as possible).

But I can't seem to find anyway to make $bar->method(); see the
appropriate value of $foo depending on whether $bar is an object of
type A or C. Am I going to have to have a method (or AUTOMETHOD) to
copy $foo into the B namespace when method is called? Or is there a
more elegant way of handling this? [As a note, in actuality, I'm
dealing with a %foo rather than a $foo].