Split function

Another script that I'm forever tracking down.

CREATE FUNCTION [dbo].[fn_Split] (
  @arr AS VARCHAR(MAX)
  , @sep AS CHAR(1)
)
RETURNS TABLE
AS
RETURN

  SELECT n - Len(REPLACE(LEFT(@arr,n),@sep,'')) + 1 AS pos
    ,CAST(Substring(@arr,n,Charindex(@sep,@arr + @sep,n) - n) AS INT) AS Element
  FROM (SELECT @arr AS arr) AS a
    JOIN dbo.nums
     ON n <= Len(@arr)
     AND Substring(@sep + @arr,n,1) = @sep