He could not help noticing that Dick, busy gouging under his fingernails with a fork prong, was uninterested in his dream.
Something that is really striking to me is that Perry's guilt dream is of him being specifically eaten by a snake with Dick is stuffing himself with food. If Perry did not associate himself with Dick and go along with his plan to rob (and ultimately kill) the Clutters, then he could have been fine. Since Dick solidified his fate and downfall, is he Perry's snake?