my %label = (
   one   => 'foo',
   two   => 'bar',
   three => 'baz',
);

##</code><code>##

print checkbox_group(
      -name   => 'checkbox',
      -values => [keys %label],
      -labels => \%label,
);

##</code><code>##

# create an array whose keys all have values 'no'
my %checkbox = map { $_ => 'no' } keys %label;

# update each found key's value to 'yes'
$checkbox{$_} = 'yes' for param('checkbox');

##</code><code>##

#!/usr/bin/perl -T

use strict;
use warnings;
use CGI qw(:standard);

my %label = (
        one   => 'foo',
        two   => 'bar',
        three => 'baz',
);

print header,
        start_html('checkbox test'),
        start_form,
        checkbox_group(
                -name   => 'checkbox',
                -values => [keys %label],
                -labels => \%label,

        ),
        submit('go'),
        end_form,
;

if (param('go')) {
        my %checkbox = map { $_ => 'no' } keys %label;
        $checkbox{$_} = 'yes' for param('checkbox');

        print table({border=>1},
                Tr(th[qw(Var Val)]),
                map Tr(td[$_,$checkbox{$_}]), keys %checkbox
        );
}