Presuming you mean that you're adding a row which duplicates the key and value from another row you're not going to change your hash. If you've seen a key "foo" with a value "up", setting $hash{ "foo" } = "up" again doesn't really change anything in %hash. Hashes are unordered and maintain a single value for each key slot. If you need the count of rows with a particular value then count them as you read things.

my %counts_per_value;

  [... inside your while loop ...]
  $hash{ $first } = $third;
  $counts_per_value{ $third }++;
  [...]

for my $value ( sort keys %counts_per_value ) {
  say qq{$value => $counts_per_value{ $value };
}
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