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";
    }
  }
}