Batch-merging files, how?

Hi. I have two sets of images with the same size and names (but with different content), located in two different folders. I want to overlay and flatten all pairs with corresponding names (that is, image1.png from set 1 with image1.png from set 2, and so on). Actions obviously won't do it all, so some script is in order. My scripting skills are nil. Thanks for any help.