combine subnets

supernet.pl

#!/usr/bin/env perl -w
use strict;

package CIDRs {
    sub new { bless +{}, shift }

    sub add {
        my ($self, $cidr) = @_;
        my ($ipv4, $w) = split '/', $cidr;
        my $b = (hex join '', map { sprintf '%02X', $_ } split /\./, $ipv4) >> 32 - $w;
        while (delete $self->{$w}->{$b ^ 1}) { $w--; $b >>= 1 }
        ++$self->{$w}->{$b};
    }

    sub list {
        my $self = shift;
        my @list = map  { join('.', map hex, sprintf('%08X', $$_[0]) =~ /../g) . '/' . $$_[1] }
                   sort { $a->[0] <=> $b->[0] }
                   map  { my $w = $_; map { [ $_ << 32 - $w, $w ] } keys %{$self->{$w}} }
                   keys %$self;
        wantarray ? @list : \@list;
    }
}

package main {
    my $c = CIDRs->new();
    while (<>) {  
        chomp;
        $c->add($_);  # '192.168.0.0/24'
    }
    print "$_\n" for $c->list;
}