use CGI::Pretty qw(:standard);

if (param('chklstCC:0')) {
   print header, param('chklstCC:0');
}
else {
   print header,start_html,start_form,
      checkbox_group(
         -name=>'chklstCC:0',
         -values=>[qw(Visa MasterCard Discover)],
      ),
      submit('go'), end_form, end_html,
   ;
}