anchor.diff:      {#k_guard{anno=#k{us=Gus,ns=[],a=A},clauses=Gs1},Gus,St1};
   umatch(#k_guard_clause{anno=A,guard=G0,body=B0}, Br, St0) ->
       %%ok = io:fwrite("~w: ~p~n", [?LINE,G0]),
  -    {G1,Gu,St1} = uguard(G0, St0#kern{guard_refc=St0#kern.guard_refc+1}),
  +    {G1,Gu,St1} = uexpr(G0, {break,[]},
  +			St0#kern{guard_refc=St0#kern.guard_refc+1}),
       %%ok = io:fwrite("~w: ~p~n", [?LINE,G1]),
       {B1,Bu,St2} = umatch(B0, Br, St1#kern{guard_refc=St1#kern.guard_refc-1}),
       Used = union(Gu, Bu),
  
positive.code: 	false ->
  	    {#k_break{anno=#k{us=Au,ns=[],a=A},args=As},Au,St}
      end;
  ubody(#ivalues{anno=A,args=As}, {guard_break,_Vbs}, St) ->
      Au = lit_list_vars(As),
      {#k_guard_break{anno=#k{us=Au,ns=[],a=A},args=As},Au,St};
  ubody(E, return, St0) ->
      %% Enterable expressions need no trailing return.
      case is_enter_expr(E) of
  
negative.code:     {#k_receive_accept{anno=#k{us=[],ns=[],a=A}},[],St};
  uexpr(#k_receive_next{anno=A}, _, St) ->
      {#k_receive_next{anno=#k{us=[],ns=[],a=A}},[],St};
  uexpr(#k_try{anno=A,arg=A0,vars=Vs,body=B0,evars=Evs,handler=H0}=Try,
        {break,Rs0}=Br, St0) ->
      case is_in_guard(St0) of
  	true ->
  	    {[#k_var{name=X}],#k_var{name=X}} = {Vs,B0}, %Assertion.
  	    #k_atom{val=false} = H0,		%Assertion.
  	    {A1,Bu,St1} = uexpr(A0, Br, St0),
  	    {Try#k_try{anno=#k{us=Bu,ns=lit_list_vars(Rs0),a=A},
  		       arg=A1,ret=Rs0},Bu,St1};
  	false ->
  	    {Avs,St1} = new_vars(length(Vs), St0),
  	    {A1,Au,St2} = ubody(A0, {break,Avs}, St1),
  	    {B1,Bu,St3} = ubody(B0, Br, St2),
  	    {H1,Hu,St4} = ubody(H0, Br, St3),
  	    {Rs1,St5} = ensure_return_vars(Rs0, St4),
  	    Used = union([Au,subtract(Bu, lit_list_vars(Vs)),
  			  subtract(Hu, lit_list_vars(Evs))]),
  	    {#k_try{anno=#k{us=Used,ns=lit_list_vars(Rs1),a=A},
  		    arg=A1,vars=Vs,body=B1,evars=Evs,handler=H1,ret=Rs1},
  	     Used,St5}
      end;
  uexpr(#k_try{anno=A,arg=A0,vars=Vs,body=B0,evars=Evs,handler=H0},
        return, St0) ->
      {Avs,St1} = new_vars(length(Vs), St0),	%Need dummy names here
  