anchor.diff:  , withPerl530 ? false, perl530
   , withPerl532 ? true, perl532
   , withPerldevel ? false, perldevel
  -, withRuby_2_5 ? false, ruby_2_5
   , withRuby_2_6 ? true, ruby_2_6
   , withRuby_2_7 ? false, ruby_2_7
   , withSSL ? true, openssl ? null
  
positive.code:     ${optionalString withPerl530    "./configure perl   --module=perl530  --perl=${perl530}/bin/perl"}
      ${optionalString withPerl532    "./configure perl   --module=perl532  --perl=${perl532}/bin/perl"}
      ${optionalString withPerldevel  "./configure perl   --module=perldev  --perl=${perldevel}/bin/perl"}
      ${optionalString withRuby_2_5   "./configure ruby   --module=ruby25   --ruby=${ruby_2_5}/bin/ruby"}
      ${optionalString withRuby_2_6   "./configure ruby   --module=ruby26   --ruby=${ruby_2_6}/bin/ruby"}
      ${optionalString withRuby_2_7   "./configure ruby   --module=ruby27   --ruby=${ruby_2_7}/bin/ruby"}
    '';
  
negative.code:     ++ optional withPerl530 perl530
      ++ optional withPerl532 perl532
      ++ optional withPerldevel perldevel
      ++ optional withRuby_2_6 ruby_2_6
      ++ optional withRuby_2_7 ruby_2_7
      ++ optional withSSL openssl;
  