# <input type="checkbox" name="search_first_class">
# <input type="checkbox" name="search_economy_class">

my $search_first_class   = $cgi->param('search_first_class');
my $search_economy_class = $cgi->param('search_economy_class');

warn("Classes to search:"
   . ($search_first_class   ? ' First'   : '')
   . ($search_economy_class ? ' Economy' : '')
) if $DEBUG;