Displaying error in blade with error key

I am returning the custom error using return back()->withErrors() approach, exactly like this:

return back()->withErrors([
    'A' => 'XXX',
    'B' => 'YYY
])

Now, if I can use in my blade, it shows that the errors are returned like so:

ViewErrorBag {#208 ▼
  #bags: array:1 [▼
    "default" => MessageBag {#209 ▼
      #messages: array:2 [▼
        "A" => array:1 [▼
          0 => "XXX"
        ]
        "B" => array:1 [▼
          0 => "YYY"
        ]
      ]
      #format: ":message"
    }
  ]
}

If I try using , it returns an array, however I don't want to access it through the array.

What I want is to be able to use its key and return the error by the key

What is the proper way of achieving this?

via Chebli Mohamed