anchor.diff:  
   stdenv.mkDerivation rec {
     name = "${pname}-${version}";
  -  version = "${major}.0";
     pname = "htslib";
  -  major = "1.6";
  +  version = "1.6";
   
     src = fetchurl {
  -    url = "https://github.com/samtools/htslib/releases/download/${major}/htslib-${major}.tar.bz2";
  +    url = "https://github.com/samtools/htslib/releases/download/${version}/${name}.tar.bz2";
       sha256 = "1jsca3hg4rbr6iqq6imkj4lsvgl8g9768bcmny3hlff2w25vx24m";
     };
   
  -  propagatedNativeBuildInputs = [ perl ];
  +  # perl is only used during the check phase.
  +  nativeBuildInputs = [ perl ];
   
     buildInputs = [ zlib bzip2 lzma curl ];
   
  
positive.code: 
    installFlags = "prefix=$(out)";
  
    enableParallelBuilding = true;
  
    doCheck = true;
  
    preCheck = ''
      find test -name "*.pl" -exec sed -ie 's|/usr/bin/\(env[[:space:]]\)\{0,1\}perl|${perl}/bin/perl|' {} +
    '';
  
    meta = with stdenv.lib; {
      description = "A C library for reading/writing high-throughput sequencing data";
  
negative.code:     maintainers = [ maintainers.mimadrid ];
    };
  }
  