>>244
split = split' [] ""
split' acc buff "" = reverse $ reverse buff :acc
split' acc buff (x:xs)
| x == '?' = split' (reverse buff :acc) "" xs
| otherwise = split' acc (x:buff) xs

main = print $ split "213?46464?698"

こんなもんだろ。既に区切った語のリストをaccに蓄積して
今読んでる途中の語はbuffに蓄積してやる（適宜reverseで順番を直す）