for my $key ( sort keys %title ) {

##</code><code>##

# This will sort by title, then by topic id
sub by_course_and_title {
  return $title{$a}{il2e002_course_title_x} cmp title{$b}{il2e002_course_title_x} ||
         $title{$a}{il2e002_topic_id_k} cmp title{$b}{il2e002_topic_id_k};
}
for my $key ( sort &by_course_and_title keys %title ) {

##</code><code>##

for my $foo ( @foo ) {
    # Do something interesting
}