I wrote the following recently for a similar purpose:

sub walk_oo_tree
{
    my $obj = shift;

    my $class = ref $obj ? ref $obj : $obj;

    my @class_list = ();

    unless ($skip_class_map{$class})
    {
        NO_STRICT_REFS_ZONE:
        {
            no strict 'refs';
            @class_list = ($class, map { @{walk_oo_tree($_)} } @{join(
+'::', $class, 'ISA')});
            use strict 'refs';
        }
    }

    return \@class_list;
}
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The %skip_class_map (in my implementation) was global (our) and evaluated to (UNIVERSAL => 1, AUTOLOAD => 1).

Note: you can pass this a class name or an object of the required class.

Finally, to head off comments re the 'NO_STRICT_REFS_ZONE:' block: the label, block and use are not necessary. I prefer defensive programming to surprises.

Regards,