[erlang-questions] variable unsafe just in macros

[Lasaro]

Sorry, I sent the message before it was ready (twice!). The question
was
why does this definition gives me a "variable 'Param' unsafe in
'case'".

-define(debug,true).

-ifdef(debug).
-define(DEBUG(Msg),
case Msg of
         [] ->
             io:format("{~p@~p:~p}", [?MODULE,?LINE,self()]);
         [[_|_]=Format, [_|_]=Param] ->
             io:format(lists:append(["{~p@~p:~p} ",Format]), [?MODULE,?
LINE,self()|Param]);
         [_|_] ->
             io:format("{~p@~p:~p} "++Msg, [?MODULE,?LINE,self()]);
         _ ->
             io:format("{~p@~p:~p} wrong debug call", [?MODULE,?
LINE,self()])
     end).
-else.
-define(DEBUG(_M), true).
-endif.

but this one does not?

-define(debug,true).

-ifdef(debug).
deb(Msg)->
     case Msg of
         [] ->
             io:format("{~p@~p:~p}", [?MODULE,?LINE,self()]);
         [[_|_]=Format, [_|_]=Param] ->
             io:format(lists:append(["{~p@~p:~p} ",Format]), [?MODULE,?
LINE,self()|Param]);
         [_|_] ->
             io:format("{~p@~p:~p} "++Msg, [?MODULE,?LINE,self()]);
         _ ->
             io:format("{~p@~p:~p} wrong debug call", [?MODULE,?
LINE,self()])
     end.

-define(DEBUG(Msg), deb(Msg)).
-else.
-define(DEBUG(_M), true).
-endif.

Cheers.
Lásaro