diff --git a/experiments/erlang/.gitignore b/experiments/erlang/.gitignore
new file mode 100644
index 0000000..c85682e
--- /dev/null
+++ b/experiments/erlang/.gitignore
@@ -0,0 +1,2 @@
+ebin
+erl_crash.dump
diff --git a/experiments/erlang/Makefile b/experiments/erlang/Makefile
new file mode 100644
index 0000000..61a938b
--- /dev/null
+++ b/experiments/erlang/Makefile
@@ -0,0 +1,17 @@
+all: compile
+
+compile:
+	./rebar compile
+
+clean:
+	./rebar clean
+	-rmdir ebin
+
+veryclean: clean
+	rm -rf rel
+	rm -f erl_crash.dump
+
+run: compile
+	erl -pa ebin \
+		-boot start_sasl \
+		-run hop_demo start localhost
diff --git a/experiments/erlang/rebar b/experiments/erlang/rebar
new file mode 100755
index 0000000..dc66e87
Binary files /dev/null and b/experiments/erlang/rebar differ
diff --git a/experiments/erlang/src/hop.app.src b/experiments/erlang/src/hop.app.src
new file mode 100644
index 0000000..314a851
--- /dev/null
+++ b/experiments/erlang/src/hop.app.src
@@ -0,0 +1,8 @@
+%% -*- erlang -*-
+{application, hop,
+ [{description, "Hop"},
+  {vsn, "0.0.1"},
+  {registered, []},
+  {applications, [kernel,
+                  stdlib]},
+  {env, []}]}.
diff --git a/experiments/erlang/src/sexp.erl b/experiments/erlang/src/sexp.erl
new file mode 100644
index 0000000..9a93989
--- /dev/null
+++ b/experiments/erlang/src/sexp.erl
@@ -0,0 +1,122 @@
+%% Copyright 2010, 2011, 2012 Tony Garnock-Jones <tonygarnockjones@gmail.com>.
+%%
+%% This file is part of Hop.
+%%
+%% Hop is free software: you can redistribute it and/or modify it
+%% under the terms of the GNU General Public License as published by
+%% the Free Software Foundation, either version 3 of the License, or
+%% (at your option) any later version.
+%%
+%% Hop is distributed in the hope that it will be useful, but WITHOUT
+%% ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+%% or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+%% License for more details.
+%%
+%% You should have received a copy of the GNU General Public License
+%% along with Hop.  If not, see <http://www.gnu.org/licenses/>.
+
+-module(sexp).
+%% SPKI SEXP.
+
+-export([lex_state/0, lex/1, lex/2]).
+-export([parse_state/0, parse/1, parse/2]).
+-export([format/1, format_iolist/1]).
+
+%% Lexer states
+-record(init, {}).
+-record(str, {remaining, pieces_rev}).
+-record(strlen, {value}).
+
+%% Parser states
+-record(parser, {lexer, stack}).
+
+-define(ZERO, 48).
+-define(NINE, 57).
+
+lex_state() ->
+    #init{}.
+
+lex(Chunk) ->
+    lex(Chunk, lex_state()).
+
+lex(<<"(", Rest/binary>>, State = #init{}) ->
+    {Events, FinalState} = lex(Rest, State),
+    {[open | Events], FinalState};
+lex(<<")", Rest/binary>>, State = #init{}) ->
+    {Events, FinalState} = lex(Rest, State),
+    {[close | Events], FinalState};
+lex(<<"[", Rest/binary>>, State = #init{}) ->
+    {Events, FinalState} = lex(Rest, State),
+    {[hint_open | Events], FinalState};
+lex(<<"]", Rest/binary>>, State = #init{}) ->
+    {Events, FinalState} = lex(Rest, State),
+    {[hint_close | Events], FinalState};
+lex(<<D, Rest/binary>>, #init{}) when D >= ?ZERO andalso D =< ?NINE ->
+    lex(Rest, #strlen{value = D - ?ZERO});
+lex(<<X, Rest/binary>>, State = #init{}) when X =< 32 ->
+    lex(Rest, State);
+lex(<<D, Rest/binary>>, #strlen{value = V}) when D >= ?ZERO andalso D =< ?NINE ->
+    lex(Rest, #strlen{value = V * 10 + D - ?ZERO});
+lex(<<":", Rest/binary>>, #strlen{value = V}) ->
+    lex(Rest, #str{remaining = V, pieces_rev = []});
+lex(Chunk, #str{remaining = Len, pieces_rev = PiecesRev}) ->
+    case Chunk of
+        <<Piece:Len/binary, Rest/binary>> ->
+            {Events, FinalState} = lex(Rest, #init{}),
+            {[{str, iolist_to_binary(lists:reverse([Piece | PiecesRev]))} | Events], FinalState};
+        _ ->
+            {[], #str{remaining = Len - size(Chunk), pieces_rev = [Chunk | PiecesRev]}}
+    end;
+lex(<<>>, State) ->
+    {[], State}.
+
+parse_state() ->
+    #parser{lexer = lex_state(), stack = []}.
+
+parse(Chunk) ->
+    Inert = parse_state(),
+    case parse(Chunk, Inert) of
+        {Terms, Inert} -> {ok, Terms, Inert};
+        {Terms, Other} -> {more, Terms, Other}
+    end.
+
+parse(Chunk, #parser{lexer = Lexer, stack = Stack}) ->
+    {Events, NewLexer} = lex(Chunk, Lexer),
+    {Terms, NewStack} = parse_events(Events, Stack),
+    {Terms, #parser{lexer = NewLexer, stack = NewStack}}.
+
+parse_events([open | Rest], Stack) ->
+    parse_events(Rest, [[] | Stack]);
+parse_events([close | Rest], [AccRev]) when is_list(AccRev) ->
+    {Terms, NewStack} = parse_events(Rest, []),
+    {[lists:reverse(AccRev) | Terms], NewStack};
+parse_events([close | Rest], [AccRev, AccRevOuter | Stack]) when is_list(AccRev) ->
+    parse_events(Rest, [[lists:reverse(AccRev) | AccRevOuter] | Stack]);
+parse_events([hint_open | Rest], Stack) ->
+    parse_events(Rest, [hint | Stack]);
+parse_events([{str, Bin} | Rest], [hint | Stack]) ->
+    parse_events(Rest, [{hint, Bin} | Stack]);
+parse_events([hint_close | Rest], Stack = [{hint, _} | _]) ->
+    parse_events(Rest, Stack);
+parse_events([{str, BodyBin} | Rest], [{hint, HintBin} | Stack]) ->
+    {Terms, NewStack} = parse_events(Rest, Stack),
+    {[{HintBin, BodyBin} | Terms], NewStack};
+parse_events([{str, Bin} | Rest], Stack = []) ->
+    {Terms, NewStack} = parse_events(Rest, Stack),
+    {[Bin | Terms], NewStack};
+parse_events([{str, Bin} | Rest], [AccRev | Stack]) when is_list(AccRev) ->
+    parse_events(Rest, [[Bin | AccRev] | Stack]);
+parse_events([], Stack) ->
+    {[], Stack}.
+
+format(Sexp) ->
+    iolist_to_binary(format_iolist(Sexp)).
+
+format_bin(Bin) -> [integer_to_list(size(Bin)), $:, Bin].
+
+format_iolist(Bin) when is_binary(Bin) ->
+    format_bin(Bin);
+format_iolist({H, B}) when is_binary(H) andalso is_binary(B) ->
+    [$[, format_bin(H), $], format_bin(B)];
+format_iolist(Sexps) when is_list(Sexps) ->
+    [$(, [format_iolist(Sexp) || Sexp <- Sexps], $)].