anchor.diff:  { stdenv, fetchurl, perlPackages, wrapGAppsHook,
  +  # libs
     librsvg, sane-backends, sane-frontends,
  -  imagemagick, libtiff, djvulibre, poppler_utils, ghostscript, unpaper,
  -  xvfb_run, hicolor-icon-theme, liberation_ttf, file, pdftk }:
  +  # runtime dependencies
  +  imagemagick, libtiff, djvulibre, poppler_utils, ghostscript, unpaper, pdftk,
  +  # test dependencies
  +  xvfb_run, liberation_ttf, file, tesseract }:
   
   with stdenv.lib;
   
   perlPackages.buildPerlPackage rec {
     pname = "gscan2pdf";
  -  version = "2.3.0";
  +  version = "2.5.5";
   
     src = fetchurl {
       url = "mirror://sourceforge/gscan2pdf/${version}/${pname}-${version}.tar.xz";
  -    sha256 = "0mcsmly0j9pmyzh6py8r6sfa30hc6gv300hqq3dxj4hv653vhkk9";
  +    sha256 = "0gfhjmv768hx2l3jk2mjhh1snkgkaddgw70s14jq8kxhhzvhlmv8";
     };
   
     nativeBuildInputs = [ wrapGAppsHook ];
  
positive.code:       --prefix PATH : "${djvulibre}/bin" \
        --prefix PATH : "${poppler_utils}/bin" \
        --prefix PATH : "${ghostscript}/bin" \
        --prefix PATH : "${unpaper}/bin"
    '';
  
    enableParallelBuilding = true;
  
negative.code:   outputs = [ "out" "man" ];
  
    checkInputs = [
      imagemagick
      libtiff
      djvulibre
      poppler_utils
      ghostscript
      unpaper
      pdftk
  
      xvfb_run
      file
      tesseract # tests are expecting tesseract 3.x precisely
    ];
  
    checkPhase = ''
  