my @original_array = qw(5, 100, 2, 8, 40);
my @sequence;
my @ordered = sort @original_array;

for (my $y = 0; $y < scalar @ordered; $y++) {
  for (my $x = 0; $x < scalar @ordered; $x++) {
    push @sequence, $x + 1
      if ($ordered[$x] == $original_array[scalar @sequence]);
  }
}
my @letter_sequence = map { local $_ = $_; tr/1-9/a-h/; $_ } @sequence;