changecase_server.erl

-module(changecase_server).
-export([start/0, loop/0]).

start() ->
    spawn(changecase_server, loop, []).

loop() ->
    receive
        % pattern matching
        {Client, {Str, uppercase}} -> 
            Client ! {self(), string:to_upper(Str)};
        {Client, {Str, lowercase}} ->
            Client ! {self(), string:to_lower(Str)}
    end,
    loop().