anchor.diff:    postInstall = ''
       substituteInPlace $out/bin/znapzend --replace "${perl}/bin/perl" \
         "${perl}/bin/perl \
  -      -I${Mojolicious-6-46}/${perl.libPrefix} \
  +      -I${Mojolicious-8-35}/${perl.libPrefix} \
         -I${perlPackages.TAPParserSourceHandlerpgTAP}/${perl.libPrefix} \
  -      -I${MojoIOLoopForkCall-0-17}/${perl.libPrefix} \
  +      -I${MojoIOLoopForkCall-0-20}/${perl.libPrefix} \
         -I${perlPackages.IOPipely}/${perl.libPrefix} \
         "
       substituteInPlace $out/bin/znapzendzetup --replace "${perl}/bin/perl" \
         "${perl}/bin/perl \
  -      -I${Mojolicious-6-46}/${perl.libPrefix} \
  +      -I${Mojolicious-8-35}/${perl.libPrefix} \
         -I${perlPackages.TAPParserSourceHandlerpgTAP}/${perl.libPrefix} \
  -      -I${MojoIOLoopForkCall-0-17}/${perl.libPrefix} \
  +      -I${MojoIOLoopForkCall-0-20}/${perl.libPrefix} \
         -I${perlPackages.IOPipely}/${perl.libPrefix} \
         "
       substituteInPlace $out/bin/znapzendztatz --replace "${perl}/bin/perl" \
         "${perl}/bin/perl \
  -      -I${Mojolicious-6-46}/${perl.libPrefix} \
  +      -I${Mojolicious-8-35}/${perl.libPrefix} \
         -I${perlPackages.TAPParserSourceHandlerpgTAP}/${perl.libPrefix} \
  -      -I${MojoIOLoopForkCall-0-17}/${perl.libPrefix} \
  +      -I${MojoIOLoopForkCall-0-20}/${perl.libPrefix} \
         -I${perlPackages.IOPipely}/${perl.libPrefix} \
         "
     '';
  
positive.code:     sha256 = checksum;
    };
  
    buildInputs = [ wget perl MojoIOLoopForkCall-0-17 perlPackages.TAPParserSourceHandlerpgTAP ];
  
    nativeBuildInputs = [ autoconf automake ];
  
    preConfigure = ''
      sed -i 's/^SUBDIRS =.*$/SUBDIRS = lib/' Makefile.am
  
negative.code: { stdenv, fetchFromGitHub, fetchurl, perl, perlPackages, wget, autoconf, automake, autoreconfHook }:
  
  let
    # when upgrade znapzend, check versions of Perl libs here: https://github.com/oetiker/znapzend/blob/master/cpanfile
    # pinned versions are listed at https://github.com/oetiker/znapzend/blob/master/thirdparty/cpanfile-5.26.1.snapshot
    Mojolicious-8-35 = perlPackages.buildPerlPackage rec {
      pname = "Mojolicious";
      version = "8.35";
      src = fetchurl {
        url = "mirror://cpan/authors/id/S/SR/SRI/${pname}-${version}.tar.gz";
        sha256 = "1bll0ahh5v1y3x0ql29klwsa68cj46wzqc385srsnn2m8kh2ak8h";
      };
    };
    MojoIOLoopForkCall-0-20 = perlPackages.buildPerlModule rec {
      pname = "Mojo-IOLoop-ForkCall";
      version = "0.20";
      src = fetchurl {
        url = "mirror://cpan/authors/id/J/JB/JBERGER/${pname}-${version}.tar.gz";
        sha256 = "19pih5x0ayxs2m8j29qwdpi6ky3w4ghv6vrmax3ix9r59hj6569b";
      };
      propagatedBuildInputs = [ perlPackages.IOPipely Mojolicious-8-35 ];
    };
  
    version = "0.20.0";
    checksum = "15lb5qwksa508m9bj6d3n4rrjpakfaas9qxspg408bcqfp7pqjw3";
  in
  stdenv.mkDerivation {
    pname = "znapzend";
  