anchor.diff:    checkFlags = map (T: "TESTNUM=${T}") (lib.stringToCharacters "ABCDEVW");
   
     # XXX: think/discuss about this, also with respect to nixos vs nix-on-X
  -  postInstall = lib.optionalString stdenv.isLinux ''
  +  postInstall = ''
       make install.info install.html
  -    '' + ''
       mkdir -p $out/etc/
       cat > $out/etc/zprofile <<EOF
   if test -e /etc/NIXOS; then
  
positive.code: stdenv.mkDerivation {
    pname = "zsh";
    inherit version;
  
    src = fetchurl {
      url = "mirror://sourceforge/zsh/zsh-${version}.tar.xz";
  
negative.code:     mv $out/etc/zprofile $out/etc/zprofile_zwc_is_used
  
      rm $out/bin/zsh-${version}
      mkdir -p $out/share/doc/
      mv $out/share/zsh/htmldoc $out/share/doc/zsh-$version
    '';
    # XXX: patch zsh to take zwc if newer _or equal_
  
  