use 5.010;
use strict;
use warnings;

my %ips;
while (<$in_fh>)
{
	push @{ $ips{"$1.$2.$3"} }, "$1.$2.$3.$4"
		if /^(\d+)\.(\d+)\.(\d+)\.(\d+)/;
}

say $ips{$_}[rand @{$ips{$_}}]
	for sort keys %ips;