Net::Netmask parses and understands IPv4 and IPv6 CIDR blocks.
 It's built with an object-oriented interface,
 with functions being methods that operate on a Net::Netmask object.
 .
 These methods provide
 nearly all types of information about a network block
 that you might want.
 .
 There are also functions to insert a network block into a table
 and then later lookup network blocks by IP address using 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.
 .
 All functions understand both IPv4 and IPv6.
 Matches, finds, etc, will always return false
 when an IPv4 address is matched against an IPv6 address.