Below is code I use for checkboxgroups. The code offered by hbo can still be used as it provides the necessary array of @weekday which you can use in my code below. Additionally if you wanted to just select a specific day set @selected to [$weekday[$num]] at the beginning and remove the where $num would represent the day of the week. I hope this code serves as a guide to help you to your own solution, unfortunately I'm at work at the moment and can't dedicate the time to writing the exact code for you. This should be pretty close I think without testing.

## whatever @selected is set to at the beginning
## is how your checkboxgroup will appear on loading
## Choose between one of these two lines
#my @selected = @weekday;          ##--> to select all
#my @selected = ($weekday[#a number]);    ##--> to select one

foreach my $selected_day (@weekday) {
    my $checkbuttongroup = $rF->CheckbuttonGroup (
                                    -list => [ $selected_day ],
                                    -orientation => 'vertical',
                                    -variable => \@selected,
                                    -font => 'bold',
                            )->pack(-anchor => 'nw',
                                -side => 'top',
                                );
}
[download]

Update: I should add that when you run the program whatever boxes you check is what @selected will contain. Eg. Monday, Wednesday etc. You can check it by using a "print $_ for @selected" on a button callback.

Opps Update: Sorry this is how to do it in TK. I didn't see that you wanted it for CGI. If you ever get around to TK this is how its done. :-) <grinning>