use Tie::CSV_File;
tie my @array, "Tie::CSV_File", $filename, WHITESPACE_SEPARATED;
for my $i (1 .. $#array) {
    push @good_nums, 
       $array[$i-1]->[0] * $array[$i]->[1] *
       $array[$i-1]->[1] * $array[$i]->[0];
    # Did you really want to compute 4x a multiplication ?!
}
print @good_nums;

##</code><code>##

@array = map {[split]} @array;
# instead of the first two lines of my snippet