-module(rot13).
-export([start/0]).

%% run as "# erl -noshell -s rot13 < infile"


start() ->
    run(io:get_chars('', 1)).

run(eof) ->
    init:stop();
run([Char]) ->
    io:format("~c", [rot13(Char)]),
    run(io:get_chars('', 1)).

rot13(X) when X >= $a, 
	      X <  $n;

	      X >= $A,
	      X <  $N ->
    X+13;

rot13(X) when X >= $n,
	      X <  ${;

	      X >= $N,
	      X < $[ ->
    X-13;
rot13(X) ->
    X.