If you view the source to see sub generate_form { you'll see it takes a htype option , so specify htype somehow ... check the dist tree for an example of usage (grep "radio|check|htype" https://metacpan.org/release/CGI-Ex )

if that fails study the code

        } elsif ($type eq 'radio' || $type eq 'checkbox') {
            my $e = $field->{'enum'}  || [];
            my $l = $field->{'label'} || $e;
            my $I = @$e > @$l ? $#$e : $#$l;
            for (my $i = 0; $i <= $I; $i++) {
                my $_e = $e->[$i];
                $_e =~ s/\"/&quot;/g;
                $input .= "<div class=\"option\"><input type=\"$type\"
+ name=\"$field->{'field'}\" id=\"$field->{'field'}_$i\" value=\"$_e\"
+>"
                    .(defined($l->[$i]) ? $l->[$i] : '')."</div>\n";
            }
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