Hehe... don;t know about how good an idea it is... but this seems to work and requires no secondary data structures, as you wanted.

my $hash = {
  foo => { one   =>  3 },
  bar => { two   =>  6 },
  baz => { three =>  9 },
};

print join($/,sort { $b <=> $a } 
        map { my $section = $_; 
              map { sprintf("%5d %10s %s",$hash->{$section}{$_},$secti
+on,$_) 
                  } keys %{$hash->{$section}} 
            } keys %$hash )
      ,$/;
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