The possible size of an array is only limited by how much memory you have. You may be running out of memory here. Instead of creating a huge scalar and a huge array, you might try just creating the array as you read the file:

while (<ASA>) {
    push @ASAList, split;
}
[download]

This may help enough to get the entire array into memory, but if not, you'll have to use some scheme for keeping the data on the hard disk and only reading what you need. Sounds like a good job for a tied array, maybe something in the Tie namespace on CPAN will help.