sub add {
    # check if the Big Boss is calling us...
    if( (caller(1))[3] =~ /^SomeData::/) {
        # we feel guilty, so let's hide
	return shift->SUPER::add(@_);
    }
    # ...back to our scheduled job
    my($self, $value) = @_;
    die "not a number" unless $value =~ /^\d+$/;
    $$self += $value;
}