pandoc-2.15: test/command/4054.md

```
% 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" ] ) ]
    }
  []
```