my %total_bytes;
while (<>) {
my ($source, $destination, $bytes) = split;
$total_bytes{$source}{$destination} += $bytes;
}
for my $source (sort keys %total_bytes) {
for my $destination (sort keys %{ $total_bytes{$source} }) {
print "$source => $destination:",
" $total_bytes{$source}{$destination} bytes\n";
}
print "\n";
}