Returns the index of the item that follows the array item having index index or returns the Nil object if the item having that index is last in the array. For multi-dimension arrays, the same ordering used by the allitems() (Section 5.3.6.8, “allItems”) method is used to determine the next position and the index is returned as an array of index values.
Note that the index argument may also be specified as an array of indexes.
Example 5.151. Array class - next method
a = .array~of("Fred", , "Mike", , "David")
say a~next(3) -- says: 5
