libnet-netmask-perl 1.9015-4 (i386 binary) in ubuntu precise

 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 an 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.