Thanks for the kind words, mhearse. I don't have a public GitHub or web presence, aside from my sundry answers on PerlMonks.

Also... where did you learn about bitshifting and netmasking?

I'd better not answer that one directly. :-)

Have a look at Bitwise_operation, maybe Truth_table for some background. Once you have a decent handle on that, IP subnetting (which I've only just skimmed), looks like a decent intro to IPv4 math.

Can you recommend a book?

Unfortunately, my brain's bibliography is in serious need of trie optimization. Any relatively current text on IP networking will probably be a good start, though.