#!/usr/bin/perl

use strict;
use warnings;

my %customers = (
  '1' => { '127.0.0.1'  => { foo => 1 },
           '127.0.0.2'  => { foo => 2 },
           '127.0.0.3'  => { foo => 3 },
         },
  '2' => { '127.0.0.4'  => { foo => 1 },
           '127.0.0.5'  => { foo => 2 },
           '127.0.0.6'  => { foo => 3 },
         },
  '3' => { '127.0.0.7'  => { foo => 1 },
           '127.0.0.8'  => { foo => 2 },
           '127.0.0.9'  => { foo => 3 },
         },
  '4' => { '127.0.0.10' => { foo => 1 },
           '127.0.0.20' => { foo => 2 },
           '127.0.0.30' => { foo => 3 },
         }
);

my @ids = qw( 1 2 3 4 );

foreach my $id ( @ids ) {
  foreach my $ip ( keys %{ $customers{$id} } ) {
    print "ID: $id, IP: $ip, fo: $customers{$id}{$ip}{foo}\n";
  }
}