anchor.diff:        ++ optional (vpxSupport && hasPrefix "0.8." version) ./vpxenc-0.8.17-libvpx-1.5.patch
         ;
   
  -    preConfigure = "patchShebangs doc/texi2pod.pl";
  +    postPatch = ''
  +      patchShebangs .
  +      # another shebang was hidden in a here document text
  +      substituteInPlace ./configure --replace "#! /bin/sh" "#!${bash}/bin/sh"
  +    '';
   
       configureFlags =
         assert stdenv.lib.all (x: x!=null) buildInputs;
  
positive.code: 
      # alltools to build smaller tools, incl. aviocat, ismindex, qt-faststart, etc.
      buildFlags = "all alltools install-man";
  
      postInstall = ''
        moveToOutput bin "$bin"
  
negative.code: { stdenv, fetchurl, pkgconfig, yasm, bzip2, zlib, perl, bash
  , mp3Support    ? true,   lame      ? null
  , speexSupport  ? true,   speex     ? null
  , theoraSupport ? true,   libtheora ? null
  