```
% pandoc -t native -s -M title=New
% Old
^D
Pandoc
  ( Meta { unMeta = fromList [ ( "title", MetaString "New" ) ] } ) []
```

```
% pandoc -t native -s -M foo=1 -M foo=2
^D
Pandoc
  ( Meta
    { unMeta = fromList
      [ ( "foo", MetaList [ MetaString "1", MetaString "2" ] ) ]
    }
  ) []
```