anchor.diff:  , withPHP73 ? false, php73
   , withPerl ? true, perl
   , withPerldevel ? false, perldevel
  -, withRuby_2_3 ? false, ruby_2_3
   , withRuby_2_4 ? false, ruby_2_4
   , withRuby ? true, ruby
   , withSSL ? true, openssl ? null
  
positive.code:     ${optionalString withPHP73      "./configure php     --module=php73     --config=${php73.dev}/bin/php-config  --lib-path=${php73}/lib"}
      ${optionalString withPerl       "./configure perl    --module=perl      --perl=${perl}/bin/perl"}
      ${optionalString withPerldevel  "./configure perl    --module=perl529   --perl=${perldevel}/bin/perl"}
      ${optionalString withRuby_2_3   "./configure ruby    --module=ruby23    --ruby=${ruby_2_3}/bin/ruby"}
      ${optionalString withRuby_2_4   "./configure ruby    --module=ruby24    --ruby=${ruby_2_4}/bin/ruby"}
      ${optionalString withRuby       "./configure ruby    --module=ruby      --ruby=${ruby}/bin/ruby"}
    '';
  
negative.code:     ++ optional withPHP73 php73
      ++ optional withPerl perl
      ++ optional withPerldevel perldevel
      ++ optional withRuby_2_4 ruby_2_4
      ++ optional withRuby ruby
      ++ optional withSSL openssl;
  