While I agree that it'll probably increase, for non-performance-sensitive stuff (or small lists) that doesn't really seem like a problem. And for cases where it is, the answer is the same as it has always been: profile and optimize.

Though now it's much easier to make a "matches, mismatches := slices.Split(xs, func(x whatever) bool { return x == condition })" helper, so that improvement even reduces the number of lines further.