Program Repair Shop

Special cases

     354  foreach $filesz (sort { $b <=> $a } keys %names_by_size)
        ...
     371      if ($filesz == 0) # skip files of zero length
     372      {
     373        print "$num_files_this_size files of size 0:\n    ",
     374            join ("\n    ", @{$names_by_size{$filesz}}), "\n";
     375        next;
     376      }
     377

Here we check each key to see if it is 0
Hash keys are unique
- At most one key can possibly be 0
- The whole point of hashes is to make it easy to find such a key

        { my $zeroes = delete $names_by_size{0};
          if ($zeroes) {
              print @$zeroes . " files of size 0:\n    ",
                  join ("\n    ", @$zeroes);
          }
        }

And we can remove this code from the loop
Any opportunity to simplify a three-page loop is one we should consider