Your existing code hardcodes all of the possible levels. You need to traverse the hash to whatever the appropriate depth is and then place your entry there. Try the following to see how to do it: 
#!/usr/bin/perl -w

use strict;
use Data::Dumper;

my %result;

for my $l (<DATA>) {
    my ($cod,$desc) = ($l =~/(\d*) (.*)/);
    my $hashref = \%result;
    my $partial = '';
    foreach my $layer (split //, $cod) {
        $partial .= $layer;
        $hashref = ($hashref->{$partial} ||= {});
    }
    $hashref->{0} = $desc;
}
print Dumper \%result;

__DATA__
1 ITEM
11 Sub Item 1
111 Item X
112 Item
1121 Another Item
11212 And Another Item
12 Sub Item 2

[download]
Note that before your iron down what you want your representation to be, you should try to write sample code to do the tasks that you need to do using this representation. I'm trying to figure out for what task this data structure would be convenient, and I'm having no luck. Combined with your inexperience, I'd take this as a sign that you probably need a different representation but don't know what.

In reply to Re: Generation of a Hash of Hashes by tilly
in thread Generation of a Hash of Hashes by Miguel

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