foreach my $week (sort keys %IssuesByWeek) {
        my $issues=$IssuesByWeek{$week};
        print "$week:\n\t",
              join ("\n\t", 
                map{ "$_ => $issues->{$_}" } 
                ( sort { $issues->{$b} <=> $issues->{$a} } 
                  keys %$issues )[0..4]
              ),"\n";
}