Let's say you have 3 different coupons that you want to use at Kohls. In the past you'd have to clip all 3 coupons, or download all 3 to your Passbook.
With coupon swapping, you just get one coupon (your Perpetual coupon for Kohls.) When you get to the store, use that first coupon, scan the barcode with the clerk as usual. When you are ready for the next coupon, go to the back of your pass and look for the "Replace With New Coupons" link at the very bottom of the pass back.
When you click it, you'll see a list of all the other coupons for Kohls at that time. Just choose the new coupon you want...then go back to Passbook.
Within a couple moments, Presto! You will see that Passbook was sent the new coupon and swapped it in place of your first coupon. You can swap in and out as many coupons to your pass as you want.
The point of a Perpetual coupon is that you never need more than ONE PASS per merchant. Simple, clean, and easy to use.
Note that...you might also see a button at the top of the "Replace" window, that says "Change to Master". This turns your coupon into a master pass if you click it. Of course, you can always change that master pass back to a coupon again.