anchor.diff:      "--with-perl_modules_path=lib/perl5"
     ]
       ++ optional (gd != null) "--with-http_image_filter_module"
  +    ++ optional (geoip != null) "--with-http_geoip_module"
  +    ++ optional (withStream && geoip != null) "--with-stream_geoip_module"
       ++ optional (with stdenv.hostPlatform; isLinux || isFreeBSD) "--with-file-aio"
       ++ configureFlags
       ++ map (mod: "--add-module=${mod.src}") modules;
  
positive.code:     "--with-http_realip_module"
      "--with-http_addition_module"
      "--with-http_xslt_module"
      "--with-http_geoip_module"
      "--with-http_sub_module"
      "--with-http_dav_module"
      "--with-http_flv_module"
  
negative.code: { lib, stdenv, fetchurl, fetchpatch, openssl, zlib, pcre, libxml2, libxslt
  
  , nixosTests
  , substituteAll, gd, geoip, perl
  , withDebug ? false
  