use HTML::AsSubs;
  ... # your @days gets filled in here
  my $c = HTML::CalendarMonth->new(month => $month, year => $year);
  $c->item(@days)->attr(bgcolor => 'wheat');

  # Or maybe you want a link
  my $link = 'http://www.somewhere.com/'
  foreach my $day (@days) {
    my $href = $link . "?$day";
    $c->item($day)->wrap_content(a({href => $href}));
  }