Returns the index of the first item in the array or the Nil object if the array is empty. For multi-dimension arrays, the index is returned as an array of index values.
Example 5.140. Array class - first method
a = .array~of("Mike", "Rick", "Fred", "Rick")
say a~first -- says: 1
a = .array~of(,"Mike", "Rick")
say a~first -- says: 2
