DIM Z$
Z$ = "1,2,3,4,5,666,777,88888,99999,101010101010101010"
Parse(Z$)

SUB Parse (A$)
  LOCAL Sep
  LOCAL B$
  Sep = INSTR(A$, ",")
  IF Sep > 0 THEN
    B$ = LEFT$(A$, Sep - 1)
    PRINT B$
    A$ = MID$(A$, Sep + 1, 256)
    Parse(A$) ' --- Recursive Call --- 
  ELSE
    PRINT A$
  END IF
END SUB

Result:

1
2
3
4
5
666
777
88888
99999
101010101010101010