Check over Parse or MatchSince the primary artifact produces from rat is a Result makes sense to use the verb Check over the other traditional ones that are associated with regular expressions. Match implies just a scan for a surface match. Go has Find to return results (which I have always found a bit off).
Another reason to use Check is to emphasize that there is no parsing going on, just bookmarking pointers to positions in the underlying memory of the []rune slice. Then, later people can pull out of it what they want without consuming the memory wastefully and dedicating it to sub-slices.