Hello monks! I would appreciate your enlightenment on the following. I have a tab-separated file as follows

A B n1
A B n2
A C n1
D E n2
D E n4
D F n1
[download]

and I want to count how many elements on the 3rd column does each element on the two other columns have. I.e. There are A=>3, A=>B=>2, A=>C=>1, etc. It is important for me to have the association between the first and second columns.

The easy way to solve this is just counting how many times A repeats, and how many times B repeats, etc. etc. But because I'm learning Perl, I'd like to know how to use a HoH to do this. In this regard, I built a HoH of the form

{
 A => {
   B => [
      n1,
      n2,
    ],
   C => [
      n1,
    ]
  },
 D => {
   E => [
      n2,
      n4,
    ],
   F => [
      n1,
    ]
  }
}
[download]

I know how to do this for counting the number of values in the third level, and the number of values in the second level, but how can I multiply them? Ideally, what I'd like to do is to create a key "count" with the number of "n" in the third column for each. For instance

{
 A => {
   count => 3,
   B => {
    count => 2,
    [
      n1,
      n2,
    ],
   },
   C => {
    count => 1,   
    [
      n1,
    ]
   }
  },etc.
[download]

Any tips on how to get this kind of value counting?

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