AHK: array.base

arr := StrSplit("1 2 3 4 5 6", " ")
arr.base := _Array
newArr := arr.slice(3)

for k, v in newArr
   str .= (k = 1 ? "" : ", ") . v
MsgBox, % str

class _Array
{
   slice(start:=0, end:=0)
   {

      len := this.Length()

      ; START: Adjust 1 based index, check signage, set defaults
      if (start > 0)
         begin := start - 1   ; Include starting index going forward
      else if (start < 0)
         begin := len + start  ; Count backwards from end
      else
         begin := start


      ; END: Check signage and set defaults
      ; MDN States: "to end (end not included)" so subtract one from end
      if (end > 0)
         last := end - 1
      else if (end < 0)
         last := len + end + 1 ; Count backwards from end
      else
         last := len


      results := []

      loop, % last - begin
         results.push(this[begin + A_Index])

      return results
   }
}