anchor.diff:  { stdenv, fetchurl, fetchgit, openssl, zlib, pcre, libxml2, libxslt, expat
   , rtmp ? false
   , fullWebDAV ? false
  -, syslog ? false}:
  +, syslog ? false
  +, moreheaders ? false}:
   
   let
     version = "1.4.4";
  
positive.code:     # "--with-http_perl_module"
    ] ++ stdenv.lib.optional rtmp "--add-module=${rtmp-ext}"
      ++ stdenv.lib.optional fullWebDAV "--add-module=${dav-ext}"
      ++ stdenv.lib.optional syslog "--add-module=${syslog-ext}";
  
    preConfigure = ''
      export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE -I${libxml2}/include/libxml2"
  
negative.code:     rev = "165affd9741f0e30c4c8225da5e487d33832aca3";
      sha256 = "14dkkafjnbapp6jnvrjg9ip46j00cr8pqc2g7374z9aj7hrvdvhs";
    };
  
    moreheaders-ext = fetchgit {
      url = https://github.com/agentzh/headers-more-nginx-module.git;
      rev = "refs/tags/v0.23";
      sha256 = "12pbjgsxnvcf2ff2i2qdn39q4cm5czlgrng96j8ml4cgxvnbdh39";
    };
  in
  
  stdenv.mkDerivation rec {
  