Instead of loading this data from a hash that is defined within your program, you should really be hauling this out of a file such as ISO3166 which defines the countries. The other "special" domains can be hauled out of another file. If you're feeling ambitious enough, another program would munge these two together into a single "config file".

Another problem you're likely to have is that your program wedges on the gethostbyaddr call. This will block for a long time until it gets an answer. In some cases, the DNS servers you are querying will be down, and you will not get a response. This can limit your rate of resolution to something appallingly low, like 1-2 resolves per minute. A special purpose tool such as DJB's dnsfilter program will do the lookups in parallel. This is part of the djbdns package. These sort of programs are virtually required for reversing a large set of data, such as a log-file from a Web server. dnsfilter is easy enough to use, as it takes input on STDIN.