use Data::OptList;

my $options = Data::OptList::mkopt([
				    qw(key1 key2 key3 key4),
				    key5 => { x => 1, y => 2 },
				    key5 => { a => 2, b => 4 },
				   ]);

use Data::Dumper;

warn Dumper($options);


sh-3.2$ perl try.pl
$VAR1 = [
          [
            'key1',
            undef
          ],
          [
            'key2',
            undef
          ],
          [
            'key3',
            undef
          ],
          [
            'key4',
            undef
          ],
          [
            'key5',
            {
              'y' => 2,
              'x' => 1
            }
          ],
          [
            'key5',
            {
              'a' => 2,
              'b' => 4
            }
          ]
        ];
sh-3.2$

##</code><code>##

  [
            'key5',
            [
            {
              'a' => 2,
              'b' => 4
            },
            {
              'y' => 2,
              'x' => 1
            }
            ]
          ]