anchor.diff:    buildPhase = ":";
   
     installPhase = ''
  -    for api in GL{,ES{,2,3},SC{,2}}; do
  -      pushd $api/
  -        while read header; do
  -          install -D -m644 -v $header $out/include/$(basename "$api")/$header
  -        done < <(find . -name "*.h" -printf '%P\n')
  +    local opengl_api
  +    for opengl_api in GL{,ES{,2,3},SC{,2}}; do
  +      pushd $opengl_api/
  +        local -a opengl_headers
  +        mapfile -t opengl_headers < <(find . -name '*.h' -printf '%P\n')
  +        for opengl_header in "''${opengl_headers[@]}"; do
  +          install -D -m644 -v "$opengl_header" \
  +            "$out"/include/"$(basename "$opengl_api")"/"$opengl_header"
  +        done
         popd
       done
   
  -    for xml in xml/*.xml; do
  -      install -D -m644 -v "$xml" \
  -        "$out"/share/opengl-registry/"$(basename "$xml")"
  +    local opengl_xml
  +    for opengl_xml in xml/*.xml; do
  +      install -D -m644 -v "$opengl_xml" \
  +        "$out"/share/opengl-registry/"$(basename "$opengl_xml")"
       done
     '';
   
  
positive.code: 
    src = fetchurl {
      name = "opengl-headers-${date}.tar.xz";
      multihash = "QmdguDdKPiByjdNGu5bCpsoPcHyrTXq5UoycS3hrpZMtNX";
      sha256 = "64a86c8157ebb9fcdc3adaf563d28e65ad6b0b85b9a609fad0890b5c61ccb423";
    };
  
    configurePhase = ":";
  
negative.code:       ];
  
        postPatch = ''
          patchShebangs xml/genheaders.py
  
          # Fix impure date in headers
          grep -q "time.strftime('%Y%m%d')" xml/genheaders.py
  