anchor.diff:  check_gexpr(['progn'|B], Env, L, St) -> check_gbody(B, Env, L, St);
   check_gexpr(['if'|B], Env, L, St) -> check_gif(B, Env, L, St);
   check_gexpr([call,[quote,erlang],[quote,Fun]|As], Env, L, St) ->
  -    check_gexpr([Fun|As], Env, L, St);      %Pass the buck
  -check_gexpr([call|_], _, L, St) ->          %Other calls not allowed
  +    check_gexpr([Fun|As], Env, L, St);          %Pass the buck
  +check_gexpr([call|_], _, L, St) ->              %Other calls not allowed
       illegal_guard_error(L, St);
   %% Finally the general case.
   check_gexpr([Fun|As], Env, L, St0) when is_atom(Fun) ->
  
positive.code:     gexpr_set_map(Map, As, Env, L, St);
  check_gexpr(['mupd',Map|As], Env, L, St) ->
      gexpr_update_map(Map, As, Env, L, St);
  %% check_gexpr(['map-get',Map,K], Env, L, St) ->
  %%     check_gexpr(['mref',Map,K], Env, L, St);
  check_gexpr(['map-set',Map|As], Env, L, St) ->
      check_expr(['mset',Map|As], Env, L, St);
  check_gexpr(['map-update',Map|As], Env, L, St) ->
  
negative.code: %% expr_get_map(Map, Key, Env, Line, State) -> State.
  %% expr_set_map(Map, Pairs, Line, State) -> State.
  %% expr_update_map(Args, Pairs, Line, State) -> State.
  %%  Functions for checking maps, these always return errors if system
  %%  does not support maps.
  
  -ifdef(HAS_MAPS).
  expr_map(Pairs, Env, L, St) ->
  