anchor.diff:  
     # the latest Devel version
     perldevel = common {
  -    self = perldevel;
  +    perl = pkgs.perldevel;
       buildPerl = buildPackages.perldevel;
       version = "5.29.9";
       sha256 = "017x3nghyc5m8q1yqnrdma96b3d5rlfx87vv5mi64jq0r8k6zppm";
  
positive.code: { config, lib, stdenv, fetchurl, buildPackages, callPackage
  , enableThreading ? stdenv ? glibc, makeWrapper
  }:
  
  
negative.code:     # TODO merge setup hooks
      setupHook = ./setup-hook-cross.sh;
    });
  in {
    # the latest Maint version
    perl528 = common {
      perl = pkgs.perl528;
      buildPerl = buildPackages.perl528;
      version = "5.28.2";
      sha256 = "1iynpsxdym4h76kgndmn3ykvwxhqz444xvaz8z2irsxkvmnlb5da";
  