erlang string tokenize

split.erl

-module(split).
-export([tokens/2]).
-export([len/1]).
-export([substr/3]).

tokens(String, Limiter) ->
  tokens(String, Limiter, [], []).
  
tokens([], _Limiter, Sub, Res) ->
  [lists:reverse(Sub)|Res];
  
tokens(Str, Limiter, Sub, Res) ->

  [H|T] = Str,
  Substr = lists:sublist(Str,len(Limiter)),
  
    if
      Substr == Limiter ->
        tokens(lists:sublist(Str,len(Limiter)+1, len(Str)), Limiter, [], [lists:reverse(Sub)|Res]);
      true ->
        tokens(T, Limiter, [H|Sub], Res)
    end.
    
    
len(Str) ->
  len(Str, 0).
  
len(Str,Len) ->
  case Str of
    [] -> Len;
    [_|T] -> len(T,Len+1)
  end.
  
substr(String, Start, End) ->
  substr(String, Start, End, [], 1).
  
substr(String, Start, End, Res ,Count) ->
  case String of
    [] ->
      lists:reverse(Res);
    [H|T] ->
      if 
        (Count >= Start) and (Start > 0) and (End >= Count) ->
          substr(T, Start, End,[H|Res], Count+1);
        true ->
          substr(T, Start, End, Res, Count+1)
      end
          
  end.