you're supposed to use hash references into arrays?

The data structure you're probably looking for is a hash, where each value is a reference to an individual array - a "hash of arrays". The links that Happy-the-monk provided above should explain.

But I don't see how(in example) typing in the "2" would pull up both BBB AND EEE

"Access and Printing of a HASH OF ARRAYS" in perldsc shows you some examples of how to access the data structure. It'd probably also be helpful to you if you learn about how to handle references in general, e.g. perlreftut.

To get you started, here's one way to build such a structure from the input you showed. One important concept here is autovivification, which is what causes you to be able to write @{$data{$k}} and have a reference to a new array spring into existence ("vivify") even if $data{$k} was previously undefined.

use warnings;
use strict;
my %data;
while (<DATA>) {
    chomp;
    next unless /\S/;
    my ($k,$v) = /^\s*(\S+)\s+(.+?)\s*$/;
    push @{$data{$k}}, $v;
}
use Data::Dumper;
print Dumper(\%data);
__DATA__
1 AAA 
2 BBB
3 CCC
4 DDD
2 EEE

[download]

Output:

$VAR1 = {
          '3' => [
                   'CCC'
                 ],
          '1' => [
                   'AAA'
                 ],
          '4' => [
                   'DDD'
                 ],
          '2' => [
                   'BBB',
                   'EEE'
                 ]
        };

[download]

In reply to Re: duplicate keys on hash by Anonymous Monk
in thread duplicate keys on hash by Anonymous Monk

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