{$ifdef Profile}
  {$define __TRACE__:= try }
  {$define __END__:= finally ShowMessage('Hello !'); end;}
{$else}
  {$define __TRACE__:= //}
  {$define __END__:=}
{$endif}

...
   __TRACE__
     // Somethings
    __END__
    ...

[dcc32 Error] Unit1.pas(37): E2003 Undeclared identifier: '__TRACE__'
[dcc32 Error] Unit1.pas(38): E2066 Missing operator or semicolon
[dcc32 Error] Unit1.pas(39): E2003 Undeclared identifier: '__END__'