my $url_group = $query->param('url_group');
print start_form(-action=>"test_form.pl?$url_group");
print $query->defaults;
print end_form;


##</code><code>##

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

my $query = CGI->new();
my $url_group;

if ($query->param('url_group') =~ m/^(Boston[1|2|3])$/) {
	$url_group = 'url_group=' . $query->param('url_group');
}

print header, start_html;
print "<p><b>\$query->param('url_group') = </b>\"" . $query->param('url_group') . "\"</p>";
print p("<b>The value of \$url_group is:</b> $url_group");

print start_form(-action=>"test_form.pl?$url_group");
print $query->defaults("This doesn't pass the group");
print end_form;
print end_html;

print p("<b><a href=test_form.pl?$url_group>This does work</a></b>") if ($url_group);