diff --git a/thun/gnu-prolog/Makefile b/thun/gnu-prolog/Makefile
index d8b9db4..3c702ce 100644
--- a/thun/gnu-prolog/Makefile
+++ b/thun/gnu-prolog/Makefile
@@ -1,5 +1,6 @@
 #GPLC_OPTIONS=--min-size
 GPLC_OPTIONS=--no-top-level
+#GPLC_OPTIONS=
 
 thun: thun.pl parser.pl defs.pl main.pl math.pl Makefile
 	gplc $(GPLC_OPTIONS) -o thun thun.pl parser.pl defs.pl main.pl math.pl
diff --git a/thun/gnu-prolog/main.pl b/thun/gnu-prolog/main.pl
index 5f5856a..fa4718c 100644
--- a/thun/gnu-prolog/main.pl
+++ b/thun/gnu-prolog/main.pl
@@ -20,6 +20,9 @@ Main Loop
 
 */
 
+% :- debug.
+% :- spy(thun).
+
 :- initialization(loop).
 
 loop :- prompt, line(Line), loop(Line, [], _Out).
@@ -32,9 +35,8 @@ loop( Line, In, Out) :-
   line(NextLine), !,
   loop(NextLine, S, Out).
 
-
 do_line(Line, In, Out) :-
-    phrase(joy_parse(E), Line),
+    phrase(joy_parse(E), Line), !,
     thun(E, In, Out).
 do_line(_Line, S,   S) :- write('Err'), nl.
 
diff --git a/thun/gnu-prolog/thun.pl b/thun/gnu-prolog/thun.pl
index dacef59..55672a1 100644
--- a/thun/gnu-prolog/thun.pl
+++ b/thun/gnu-prolog/thun.pl
@@ -36,7 +36,7 @@ thun([Combo|E], Si, So) :- combo(Combo, Si, S, E, Eo), thun(Eo, S, So).
 
 thun([Unknown|E], Si, So) :-
     damned_thing(Unknown),
-    write(`wtf? `),
+    write(`huh? `),
     write(Unknown), nl,
     So = [[Unknown|E]|Si].
 
@@ -82,7 +82,8 @@ func(cons, [A, B|S], [[B|A]|S]).
 func(swap, [A, B|S],  [B, A|S]).
 func(dup,     [A|S],  [A, A|S]).
 func(pop,     [_|S],        S ).
-func(sqrt, [A|S], [sqrt(A)|S]).
+
+func(sqrt, [A|S], [B|S]) :- B is sqrt(A).
 
 func(concat, [A, B|S],   [C|S]) :- append(B, A, C).
 func(flatten,   [A|S],   [B|S]) :- flatten(A, B).