I actually just solved when I peeked at the Test::Deep's code. There's an undocumented hash_each() subroutine, so the code becomes:

{
        'markets' => hash_each(
                  {
                    'primaryname' => re('.'),
                    'volume' => re('^[-+.\d]+$'),
                    'lasttradeprice' => re('^[-+.\d]+$'),
                    'marketid' => re('^\d+$'),
                    'secondarycode' => re('.'),
                    'primarycode' => re('.'),
                    'lasttradetime' => re('.'),
                    'label' => re('.'),
                    'secondaryname' => re('.'),
                    'buyorders' => array_each(
                        {
                            'quantity' => re('^[-+.\d]+$'),
                            'price' => re('^[-+.\d]+$'),
                            'total' => re('^[-+.\d]+$'),
                        },
                    ),
                    'sellorders' => array_each(
                        {
                            'quantity' => re('^[-+.\d]+$'),
                            'price' => re('^[-+.\d]+$'),
                            'total' => re('^[-+.\d]+$'),
                        },
                    ),
                    'recenttrades' => array_each(
                        {
                            'quantity' => re('^[-+.\d]+$'),
                            'price' => re('^[-+.\d]+$'),
                            'total' => re('^[-+.\d]+$'),
                            'id' => re('.'),
                            'time' => re('.'),
                        },
                    ),
               },
        ),
    }
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