anchor.diff:    # the buildNativeInputs environment variable.
     buildNativeInputs = [ ] ++ buildInputs ;
     name = "env-${name}";
  -  phases = [ "buildPhase" ];
  +  phases = [ "buildPhase" "fixupPhase" ];
     setupNew = substituteAll {
       src = ../../stdenv/generic/setup.sh;
       preHook="";
  
positive.code:       export PATH
        echo $name loaded
      EOF
      exit 0
    '';
  }
  
negative.code: 
    buildPhase = ''
      set -x
      mkdir -p "$out/dev-envs" "$out/nix-support" "$out/bin"
      s="$out/nix-support/setup-new-modified"
      cp "$setupNew" "$s"
      # shut some warning up.., do not use set -e
  