hash in hash

#!/usr/bin/perl -w

use strict;

my %hash;
my $all = "all bytes";

while(<>){
    chomp $_;
    next if(/^#|^$/);
    my ($src, $dst, $bytes) = split;
    $hash{$src}{$dst} = $bytes;
    $hash{$src}{$all} += $bytes;
}
for my $source (sort { $hash{$b}{$all} <=> $hash{$a}{$all} } keys %hash){
    print "$source    =    $hash{$source}{$all}\n";
    for my $dest (sort {$hash{$source}{$b} <=> $hash{$source}{$a}} keys %{$hash{$source}}){
        print "$source => $dest    $hash{$source}{$dest}\n";
    }
}