Hello monks!
I have a file with the following format:
ID  FIRST_NUMBER   SECOND_NUMBER
1    1               1
2    1               2
3    2               3
4    2               4
5    3               5
6    3               6
7    4               7
8    4               6
9    5               8
10    5               9
11    6              10
12    6               9

[download]
and I want to store this data in a data structure that I can easily browse. I cannot go with hashes, because neither ID nor NUMBER are unique, as you see.
By reading various tutorials, I thought that Hash of Hashes would be the thing for me, but can't seem to understand how to use it efficiently.
What I need to do is be able to read the data based on the SECOND_NUMBER. My guess is that ID, which is unique, could be of assistance, but I can't figure out how.
What I have tried is:
if($_=~/^(\d+)\t(.*)/)
{    
    $id=$1;
    $rest=$2;

    @split_rest = split(/\t/, $rest);
    $first_num=$split_rest[0];
    $second_num=$split_rest[1];

    $HoH{$id}{$first_num} = $second_num;

[download]
The HoH works OK, but how can I search it when the only thing that I am given will be the FIRST_NUMBERS and NOT the IDs? For instance, if you take line 12(last line) my target is to be able to retrieve 9 (SECOND_NUMBER) when I am given 6 (FIRST_NUMBER) but not mistake 9 for 10 (which is in the above line).

In reply to Which data structure should I use? by Anonymous Monk

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