Up in this thread you mentioned that you wabt to keep track of the the order in which you see queries and subjects. An old recipe for this is to use both an array and a hash:

my %seen_subject;
my @subjects_seen;

...
  # $s is a subject read from the excel file
  if (! $seen_subject{$s}++) {
    push(@subjects_seen, $s);
  }
...
[download]

Alternatively, look into Tie::Hash::Indexed which will return keys in the order in which they were created.