while (<LOG>) {
    my ($source, $sport, $to, $dport, $proto, $packs, $bytes) = split;
    my $key = "$source$dport";
    if ( exists( $total{$key}{from} )) {
        $total{$key}{connects}++;
        $total{$key}{bytes} += $bytes;
    }
    else {
        $total{$key} = { from => $source,
                         to => "$to:$dport",
                         bytes => $bytes,
                       };  # maybe should set 'connects => 1' as well?
    }
    $total += $bytes;
}

##</code><code>##

perl -e '$k="aaaaa";
 for $i (1..1_000_000)
 { $h1{$k}={foo=>"bar",bar=>"foo",iter=>$i}; $h1{$k}{total}++; $k++}
 sleep 20'
## consumes 344 MB in ~14.4 sec

perl -e '$k="aaaaa";
 for $i (1..1_000_000)
 {$h1{$k}={foo=>"bar",bar=>"foo",iter=>$i}; $h2{$k}++; $k++}
 sleep 20'
## consumes 352 MB in ~15.0 sec

perl -e '$k="aaaaa";
 for $i (1..1_000_000)
 {$h1{$k}={foo=>"bar",bar=>"foo"}; $h2{$k}++; $h3{$k}=$i; $k++}
 sleep 20'
## consumes 360 MB in ~16.5 sec