Net::Netmask parses and understands IPv4 CIDR blocks. It's built with an
object-oriented interface. Nearly all functions are methods that operate on a
Net::Netmask object. There are methods that provide the nearly all bits of
information about a network block that you might want. There are also functions
to put a network block into a table and then later lookup network blocks by IP
address in that table. There are functions to turn a IP address range into a
list of CIDR blocks. There are functions to turn a list of CIDR blocks into a
list of IP addresses. There is a function for sorting by text IP address.

1. build dependencies:
   1. perl-devel