The attribute hash ref can also be optional: if ref($tag->[1]) ne 'HASH', the tag has no attributes and $tag->[1] is the first child node. So position is only relative and undefs are not needed.

[ family => { name => 'Kawasaki' },
  [father => 'Yasushisa' ],
  [mother => 'Chizuko' ],
  [children =>
    [girl => 'Shiori' ],
    [boy  => 'Yasuke' ],
    [boy  => 'Kairi' ]
  ]
]
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