sub ip_to_key { sprintf "%03d", split /\./, $_[0] }

my @sortedKeys =
    sort { ip_to_key($ipaddr{$a}) cmp ip_to_key($ipaddr{$b}) }
    keys %ipaddr;

##</code><code>##

my @sortedKeys =
    map substr($_, 4),
    sort
    map pack('C4', split(/\./, $ipaddr{$_})) . $_,
    keys %ipaddr;