use DB_FILE;
my @files = glob ("*.db")  #<== about 500 of these
my @matrix; my %hash; my $key;
my $i = 0;
my $j = 0;
while ($i<=$#files) {
 tie %hash, "DB_File", $files[$i], O_CREAT | O_RDWR, 0644 or die "Could not tie to $files[$i]: $!";
 foreach $key (sort (keys (%hash))) {
  $matrix[$j]->[$i] = $hash{$key};
  $j++;  ##<== $j goes to about 6000
 }
 $j = 0;
 $i++;
}