Thanks, this is what I was looking for, something in which the numbers (255 and 233) could be changed by a human without reworking the whole pattern, and spending a not insignificant time validating that it worked correctly.

Too bad it is so long, but better that, in this case, than making changing it difficult.

Of course, there are other conditions that will surround the numbers, that are nicely done in regex form, to select which numbers get evaluated.