Make Two Weight Based Rates Available

Is there a way to have two weight based shipping rates? Specifically, I need a perishable rate and a non-perishable rate. If this is able to be done automatically with logic that would be great (ie. default non-perishable, but switch to perishable if perishable item added to cart), but if it has to be user selected at checkout that would be acceptable as well. So far I can only see an option for having one weight based rate.