DOCS-11969: fix examples in reverseArray

Author: kay-kim

source/reference/operator/aggregation/reverseArray.txt

@@ -43,24 +43,32 @@ If the argument contains subarrays, ``$reverseArray`` only operates on the top l
    :header-rows: 1
    :widths: 65 35 
 
-   * - Example
+   * - Example [#literal]_
      - Results
 
-   * - ``{ $reverseArray: [ 1, 2, 3 ] }``
+   * - ``{ $reverseArray: { $literal: [ 1, 2, 3 ] } }``
      - ``[ 3, 2, 1 ]``
 
-   * - ``{ $reverseArray: { $slice: [ [ "foo", "bar", "baz", "qux" ], 1, 2 ] } }``
+   * - ``{ $reverseArray: { $slice:  [ [ "foo", "bar", "baz", "qux" ], 1, 2 ] } } }``
      - ``[ "baz", "bar" ]``
 
    * - ``{ $reverseArray: null }``
      - ``null``
 
-   * - ``{ $reverseArray: [ ] }``
+   * - ``{ $reverseArray: { $literal: [ ] } }``
      - ``[ ]``
 
-   * - ``{ $reverseArray: [ [ 1, 2, 3 ], [ 4, 5, 6 ] ] }``
+   * - ``{ $reverseArray: { $literal: [ [ 1, 2, 3 ], [ 4, 5, 6 ] ] } }``
      - ``[ [ 4, 5, 6 ], [ 1, 2, 3 ] ]``
 
+.. [#literal]
+
+   The examples in the table take a literal argument. To avoid parsing
+   ambiguity if the literal argument is an array, you must wrap the
+   literal array in a :expression:`$literal` expression or keep the
+   outer array that designates the argument list (e.g. ``[ [ 1, 2, 3 ]
+   ]`` ) to pass in the literal array ``[1, 2, 3]``.
+
 Example
 -------