my @matrix;

while (my $file = glob "*.db") {
  tie my %hash, "DB_File", $file, O_RDONLY, 0644
    or warn("Could not read $file: $!") and next;

  # presize the array the first time
  @matrix = map [], 1 .. keys %hash
    unless @matrix;

  my $i = 0;

  for (sort keys %hash) {
    push @{ $matrix[$i++] }, $hash{$_};
  }
}