let split_on_char sep s =
let r = ref [] in
let j = ref (String.length s) in
for i = String.length s - 1 downto 0 do
if s.[i] = sep then begin
r := String.sub s (i + 1) (!j - i - 1) :: !r;
j := i
end
done;
String.sub s 0 !j :: !r