This is a quick example of the process that I had in mind as described in my previous post: 
use strict;
use warnings;
use feature qw /say/;

my %hash = (a => 1, b => 2, c => 3, d => 2, e => 5, f => 3);
my %HoA;
for my $key (keys %hash) {
    my $value = $hash{$key};
    push @{$HoA{$value}}, $key;
}
for my $key2 (keys %HoA) {
    my @keys = @{$HoA{$key2}};
    say "Keys @keys have the same value: $key2 ";
}

[download]
Which produces the following output: 
$ perl  reverse_hash.pl
Keys a have the same value: 1
Keys c f have the same value: 3
Keys b d have the same value: 2
Keys e have the same value: 5

[download]
The formatting is not exactly what you wanted, but you have the basic algorithm and the results seem correct, I leave it to you to format the output according to your needs. Don't hesitate to ask if you have any further difficulty.

Just in case you need it for better understanding, this is what the HoA looks like at the end of the first loop populating it: 

0  HASH(0x60025cbb8)
   1 => ARRAY(0x60006f210)
      0  'a'
   2 => ARRAY(0x600462490)
      0  'b'
      1  'd'
   3 => ARRAY(0x60048d1b8)
      0  'c'
      1  'f'
   5 => ARRAY(0x600495808)
      0  'e'

[download]

In reply to Re: compare text file and print occurrence of key and value by Laurent_R
in thread compare text file and print occurrence of key and value by waytoperl

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