use CGI;

my $q      = new CGI;
my $cookie = $q->cookie(-name=>'form_info') || '';

if ($cookie) {
    # you have the cookie, validate the info or whatever now
} elsif ($q->param('form_info')) {
    # you've received the form info
    # now set the cookie
    my $cookie_to_send = $q->cookie(-name=>'form_info');
    # print out header
    print $q->header(-cookie=>$cookie);
    # print out HTML header, then html document
} else {
    # no cookie or form params received
    # print out HTML form
}