[Haskell-beginners] Parse string with optional entries [Parsec]

Hi all, I'm trying to parse a string in one of the following forms using Parsec: "1\t1\t123\t456" -> desired output: [Just 1, Just 1, Just 123, Just 456] or "1\t\1\t\t456" -> desired output: [Just 1, Just 1, Nothing, Just 456] i.e., the input is a list of numbers, separated by '\t' characters, with the possibility of missing entries. I'm having troubles with the backtracking in case of missing numbers. Can anybody give me a hint? Thanks in advance, Stefan