gistfile1.hrl

-module(website_worker).
-export([behaviour_info/1, get/2]).

behaviour_info(callbacks) ->
    [{process, 1}];

behaviour_info(_) -> undefined.

get(Module, Site) -> Module:process(get_site(Site)).

get_site(Site) ->
    {ok, Socket} = gen_tcp:connect(Site, 80, [binary, {packet, 0}]),
    ok = gen_tcp:send(Socket, "GET / HTTP/1.0\r\n\r\n"),
    receive_site_data(Socket, []).

receive_site_data(Socket, SoFar) ->
    receive
      {tcp, Socket, Bin} ->
            receive_site_data(Socket, [Bin | SoFar]);
      {tcp_closed, Socket} -> binary:list_to_bin(lists:reverse(SoFar))
    end.

gistfile2.hrl

-module(test).
-export([process/1]).
-behaviour(website_worker).

process(SiteData) ->
     io:format("~p~n",[SiteData]).

gistfile3.hrl

c(website_worker).
c(test).
website_worker:get(test, "www.amazon.co.uk").
<<"HTTP/1.0 302 Found\r\nLocation: http://www.google.pl/\r\nCache-Control: private\r\nContent-Type: text/html; charset=UTF-8\r\nSet-Cookie: PREF=ID=0eb3437660e421d9:FF=0:TM=13031.......