sub _in_cidr_dns {
    my ($cidr,$addr) = @_;
    my ($start, $range) = split /\//, $cidr;
    require DNS;
    my $start_dec = DNS::aton($start);
    my $addr_dec  = DNS::aton($addr);
    return $addr_dec >= $start_dec && $addr_dec < $start_dec + 2 ** (3
+2 - $range);
}
sub _in_cidr_aton {
    my ($cidr,$addr) = @_;
    my ($start, $range) = split /\//, $cidr;
    my $start_dec = unpack("N", pack("C4", split m/\./x, $start));
    my $addr_dec  = unpack("N", pack("C4", split m/\./x, $addr));
    return $addr_dec >= $start_dec && $addr_dec < $start_dec + 2 ** (3
+2 - $range);
}
sub _in_cidr_socket {
    my ($cidr,$addr) = @_;
    my ($start, $range) = split /\//, $cidr;
    require Socket;
    my $start_dec = unpack("N*",Socket::inet_aton($start));
    my $addr_dec  = unpack("N*",Socket::inet_aton($addr));
    return $addr_dec >= $start_dec && $addr_dec < $start_dec + 2 ** (3
+2 - $range);
}
sub _in_cidr_bin {
    my ($cidr,$addr) = @_;
    my ($start, $range) = split /\//, $cidr;
    my $start_binary = _ipv4_to_32bitbinary($start);
    my $addr_binary  = _ipv4_to_32bitbinary($addr);
    my $starts_with  = substr($start_binary,0,$range);
    return $addr_binary =~ /^$starts_with/;
}

sub _ipv4_to_32bitbinary { join "", map {sprintf "%08b", $_} split /\.
+/, shift; }
[download]

         Rate    bin    dns   aton socket
bin     595/s     --   -54%   -64%   -73%
dns    1282/s   115%     --   -23%   -41%
aton   1667/s   180%    30%     --   -23%
socket 2174/s   265%    70%    30%     --