#!/usr/bin/env perl

use strict;
use warnings;

my %dat_by_id = (
    1 => {id=> 1, sn => 'a', more => 'foo'},
    2 => {id=> 2, sn => 'b', more => 'bar'},
);

my %map_sn_to_id = map +($_->{sn} => $_->{id}), values %dat_by_id;

print "SN for ID[1]:     $dat_by_id{1}{sn}\n";
print "ID for SN[b]:     $dat_by_id{$map_sn_to_id{b}}{id}\n";
print "MORE for SN[a]:   $dat_by_id{$map_sn_to_id{a}}{more}\n";

# Subsequent requirements, e.g.

my %map_more_to_id = map +($_->{more} => $_->{id}), values %dat_by_id;

print "ID for MORE[foo]: $dat_by_id{$map_more_to_id{foo}}{id}\n";
print "SN for MORE[bar]: $dat_by_id{$map_more_to_id{bar}}{sn}\n";