Xlookup to replace VLookup in complex problem

I have an old worksheet that I think I originally got from Chandoo, showing how to lookup mixed up names and return valid results. For instance, if your lookup value is "Johnson,John " and the table you're looking in has John in one column and Johnson in the other. I'm trying to figure out how to do the same thing with XLookup, and so far failing miserably. See the attached workbook. The formula in C19 I've already solved with Xlookup, but the ones in B12:B15 are the ones that are stumping me.

Any help is appreciated.