for my $acct_id (keys %customers) {
  print "Account: $acct_id\n";
  for my $ip (keys %{$customers{$acct_id}}) {
    # Do stuff here with IP
    print "IP: $ip\n";
    for my $id (keys %{$customers{$acct_id}{$ip}}) {
      print "ID: $id\n";
    }
  }
}
[download]

As I frequently seem to be specifying, I like to visualize my data structure and how it's layed out. Just to ensure you are properly visualing your data structure, you may want to take a look at Re: How can I visualize my complex data structure?. Then take advantage of Data::Dumper to ensure that you are traversing your data structures in the proper manner.

Eric

Something like this (if your %customers is a HoHoH)

#!/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";
  }
}
[download]

As madbombX mentioned, Re: How can I visualize my complex data structure? might give you some ideas. One of the nodes I reference therein, Re: I've got a hash of hashes how do i get my values out, will show you how to recursively access every element in a complex data structure.

HTH,

1. The PDSC
2. Intermediate Perl (the book)

Cheers,
Darren :)