Will prune juice give me the runs??

It has a high dependency on how much prune juice you consume. I wouldn't recommend using prune juice if you're aiming for a laxative effect, or even if you're trying to avoid one. The only way to "return to regularity" is to increase the amount of fibre on your diet. This can be easily done, just changing your breakfast cereal to something such as Shredded Wheat can make a significant difference. Increasing your fibre intake will keep you regular and not have a laxative effect if you do not exceed a certain amount. I hope this has been of some help.