anchor.diff:  in
   stdenv.mkDerivation rec {
     name = "slic3r-prusa-edition-${version}";
  -  version = "1.38.7";
  +  version = "1.39.1";
   
     enableParallelBuilding = true;
   
  
positive.code:     XMLSAX
    ]);
  
    postInstall = ''
      echo 'postInstall'
      wrapProgram "$out/bin/slic3r-prusa3d" \
  
negative.code:   src = fetchFromGitHub {
      owner = "prusa3d";
      repo = "Slic3r";
      sha256 = "0frkjgzmiy788ijkcqz3baxcrncqmk9s2vcd99hb8p2q13cg51ff";
      rev = "version_${version}";
    };
  
  