anchor.diff:      outputs = [ "out" "dev" "man" "doc" ];
   
       nativeBuildInputs =
  -      [ perl pkgconfig ]
  +      [ pkgconfig ]
  +      ++ lib.optionals (!lib.versionAtLeast version "1.12pre") [ perl ]
         ++ lib.optionals fromGit [ autoreconfHook autoconf-archive bison flex libxml2 libxslt docbook5 docbook5_xsl ];
   
       buildInputs = [ curl openssl sqlite xz ]
  
positive.code:         --replace 'std::less<Symbol>, gc_allocator<Value *>' \
                    'std::less<Symbol>, gc_allocator<std::pair<const Symbol, Value *> >'
      '';
    };
  
    nixUnstable = lib.lowPrio (common rec {
      name = "nix-1.12${suffix}";
      suffix = "pre5152_915f62fa";
      src = fetchFromGitHub {
  
negative.code:       sha256 = "0mf7y7hvzw2x5dp482qy8774djr3vzcjaqq58cp82zdil8l7kwjd";
      };
      fromGit = true;
    })) // { perl-bindings = perl-bindings { nix = nixUnstable; }; };
  
  }
  