Assigning a value to array[3, 0] did not replace any element in the array; it inserted a new element starting at index 3 instead.



array = ["Hello", "there", "AAA", 1, 2, 3]
array[3, 0] = "pie"
puts array

1.	In Ruby the first index is the start location and the second holds the count: array[start, count].
2.	array[1, 2] references two array elements, starting with the element at index 1, and this statement replaces two elements in the array, not just one:
3.	Using Two Array Indices
4.	specify where to start in the array and how many elements you want
5.	use a range:
6.	Instead of [], you can also use the slice method, another alias

Assigning a value to array[3, 0] did not replace any element in the array; it inserted a new element starting at index 3 instead. : Two Array Indices « Array « Ruby