sub listCallback {
  my ($imap, $list) = @_;
  print($list->mailbox(), "\n");
}

my %options = ();
my $imap = new Net::IMAP($host, %options);
$imap->login($user, $pass);
$imap->set_untagged_callback('list', \&listCallback);
my $response = $imap->list('', 'INBOX.*');
# function listCallback prints mailbox names