Tried this too:
iex(14)> Enum.each(list1, fn row ->
...(14)> final_list = row
...(14)> |> Enum.reduce([], fn el,acc ->
...(14)> if el >= 10 and el <= 99 do [el|acc] else acc end
...(14)> end
...(14)> )
...(14)> end
...(14)> )
Still getting the same error 
