Extract Text Differences Between Two Cells

I have to compare rule changes for a software program. The data exported gives me the new rule and the old. I want to find the differences between the new rule from the old rule and have the differences populate the adjacent cell. The rules are not identifical. I have added an example to my inquiry.

Utilizing the sample. The new rule is in Column A2 and the old rule in B2. Is there an equation I can use to extact the differences to cell C2. The answer would be "UYG,*STK,*WIREX,*BMFIX,* FBRUX,*HEPRU," I just don't want to visually examine all the different rules, just too many.

Thank you.