This is a case for normal Perl, not a module, IMHO. :) I leave it to you to update the ID's once it's sorted, but how about this:

sub by_level
{
    my $tempa =~ s/^<.*">//;
    $tempa =~ s/<\/.*>//;
    my $tempb =~ s/^<.*">//;
    $tempb =~ s/<\/.*>//;
    substr($a,0,2) cmp substr($b,0,2) ||
    $tempa cmp $tempb;
}
[download]

Update: added " to first $tempb substitution. Untested, but I think this does what you want.