anchor.diff:  
   in
   
  -stdenv.mkDerivation {
  +stdenv.mkDerivation ( {
     name = "python-2.5.4";
     
     src = fetchurl {
  
positive.code:     opensslSupport = openssl != null;
      tkSupport = (tk != null) && (tcl != null);
      libPrefix = "python2.5";
    };
  }
  
negative.code:   inherit buildInputs;
    C_INCLUDE_PATH = concatStringsSep ":" (map (p: "${p}/include") buildInputs);
    LIBRARY_PATH = concatStringsSep ":" (map (p: "${p}/lib") buildInputs);
    configureFlags = "--enable-shared --with-wctype-functions";
    
    preConfigure = ''
  