Multidimensional arrays in perl are actually arrays of references. Here's how it really works:

Suppose we have $Block[0][0][0]. That's short for $Block[0]->[0]->[0]

@Block is an array.
$Block[0] contains a reference to another array.
$Block[0]->[0] gets you to the first element in that reference, which is another reference to an array.
$Block[0]->[0]->[0] gets to the first element in that inner reference.

For details, see the perlref documentation. The bottom line is that each level can grow independently, so there is no problem with ragged array dimensions.