# (inside ncurses listbox callback)

my $listbox = shift;
my @sel = $listbox->id;

$byte2 = 0;
$byte1 = 0;

if (@sel) {
  my $code;
  $code |= 1 << $_ for @sel;
  $byte2 = $code >> 8;
  $byte1 = $code & 0xFF;
}