Populating an Array with Values

Let's say I want to create a two-dimensional array...

arr(1 to 2, 1 to 2)

...with the following values:

arr(1,1) = a
arr(2,1) = b
arr(1,2) = c
arr(2,2) = d

What is the easiest way to do it?

I would like something like this:

Dim arr(2,2) as long

arr()={{a,b},{c,d}}

Any suggestions?