$ perl make_parser.pl && perl test.pl
>> dfpm dataset add [-D] [-N <node-name>] <data-set-name-or-id> { [<volume-name-or-id>] | [<qtree-name-or-id>] | [<ossv-dir-name-or-id>] | [<storage-system-name-or-id>] | [<host-name-or-id>] }
$params = [
  'dfpm',
  {
    'type' => 'literal',
    'value' => 'dataset'
  },
  {
    'type' => 'literal',
    'value' => 'add'
  },
  {
    'type' => 'option',
    'children' => [
      {
        'type' => 'switch',
        'name' => '-D',
        'value' => undef
      }
    ]
  },
  {
    'type' => 'option',
    'children' => [
      {
        'type' => 'switch',
        'name' => '-N',
        'value' => 'node-name'
      }
    ]
  },
  {
    'type' => 'variable',
    'name' => 'data-set-name-or-id'
  },
  {
    'type' => 'option',
    'children' => [
      {
        'type' => 'alternation',
        'choices' => [
          [
            {
              'type' => 'variable',
              'name' => 'volume-name-or-id'
            }
          ],
          [
            {
              'type' => 'variable',
              'name' => 'qtree-name-or-id'
            }
          ],
          [
            {
              'type' => 'variable',
              'name' => 'ossv-dir-name-or-id'
            }
          ],
          [
            {
              'type' => 'variable',
              'name' => 'storage-system-name-or-id'
            }
          ],
          [
            {
              'type' => 'variable',
              'name' => 'host-name-or-id'
            }
          ]
        ]
      }
    ]
  }
];

>> nested-square [ [ param ] ]
$params = [
  'nested-square',
  {
    'type' => 'option',
    'children' => [
      {
        'type' => 'literal',
        'value' => 'param'
      }
    ]
  }
];

>> multi-child { foo <foo> | bar <bar> }
$params = [
  'multi-child',
  {
    'type' => 'alternation',
    'choices' => [
      [
        {
          'type' => 'literal',
          'value' => 'foo'
        },
        {
          'type' => 'variable',
          'name' => 'foo'
        }
      ],
      [
        {
          'type' => 'literal',
          'value' => 'bar'
        },
        {
          'type' => 'variable',
          'name' => 'bar'
        }
      ]
    ]
  }
];

>> partially-optimisable { <foo> | [<bar>] | [<cat>] [<dog>] }
$params = [
  'partially-optimisable',
  {
    'type' => 'option',
    'children' => [
      {
        'type' => 'alternation',
        'choices' => [
          [
            {
              'type' => 'variable',
              'name' => 'foo'
            }
          ],
          [
            {
              'type' => 'variable',
              'name' => 'bar'
            }
          ],
          [
            {
              'type' => 'option',
              'children' => [
                {
                  'type' => 'variable',
                  'name' => 'cat'
                }
              ]
            },
            {
              'type' => 'option',
              'children' => [
                {
                  'type' => 'variable',
                  'name' => 'dog'
                }
              ]
            }
          ]
        ]
      }
    ]
  }
];