Something like this?

sub {
my ($all_ids,@list);

my $tags = shift
my $cat_id = $tags->{ID};
$all_ids = $DB->table('Category')->children($cat_id);
push @$all_ids, $cat_id;
my $link_db = $DB->table('Links','CatLinks','Category');
my $condition = GT::SQL::Condition->new( 'isValidated','=','Yes','CategoryID', 'IN', \@$all_ids);
my $sth = $link_db->select($condition);
while (my $link = $sth->fetchrow_hashref) {
push @list, $link;
}

my $output;
foreach my $link (@list) {
$output .= qq~<li><a href="$CFG->{db_cgi_url}/jump.cgi?ID=$link->{ID}">$link->{'Title'}</a>~;
}

return $output;

}