anchor.diff:        '';
   
       configureFlags =
  -      ''
  -        --with-store-dir=${storeDir} --localstatedir=${stateDir} --sysconfdir=/etc
  -        --with-dbi=${perlPackages.DBI}/${perl.libPrefix}
  -        --with-dbd-sqlite=${perlPackages.DBDSQLite}/${perl.libPrefix}
  -        --with-www-curl=${perlPackages.WWWCurl}/${perl.libPrefix}
  -        --disable-init-state
  -        --enable-gc
  -      '';
  +      [ "--with-store-dir=${storeDir}"
  +        "--localstatedir=${stateDir}"
  +        "--sysconfdir=/etc"
  +        "--with-dbi=${perlPackages.DBI}/${perl.libPrefix}"
  +        "--with-dbd-sqlite=${perlPackages.DBDSQLite}/${perl.libPrefix}"
  +        "--disable-init-state"
  +        "--enable-gc"
  +      ]
  +      ++ lib.optional (!lib.versionAtLeast version "1.12pre") [
  +        "--with-www-curl=${perlPackages.WWWCurl}/${perl.libPrefix}"
  +      ];
   
       makeFlags = "profiledir=$(out)/etc/profile.d";
   
  
positive.code: { lib, stdenv, fetchurl, perl, curl, bzip2, sqlite, openssl ? null, xz
  , pkgconfig, boehmgc, perlPackages, libsodium
  , storeDir ? "/nix/store"
  , stateDir ? "/nix/var"
  }:
  
  let
  
    common = { name, src }: stdenv.mkDerivation rec {
      inherit name src;
  
      outputs = [ "out" "dev" "man" "doc" ];
  
      nativeBuildInputs = [ perl pkgconfig ];
  
      buildInputs = [ curl openssl sqlite xz ]
        ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium;
  
      propagatedBuildInputs = [ boehmgc ];
  
  
negative.code:   };
  
    nixUnstable = lib.lowPrio (common rec {
      name = "nix-1.12${suffix}";
      suffix = "pre4911_b30d1e7";
      src = fetchFromGitHub {
        owner = "NixOS";
        repo = "nix";
        rev = "b30d1e7ada0a8fbaacc25e24e5e788d18bfe8d3c";
        sha256 = "04j6aw2bi3k7m5jyqwn1vrf78br5kdfpjsj15b5r5lvxdqhlknvm";
      };
      fromGit = true;
    });
  
  }
  