if ($zip !~ /^\d+(\-\d{4})?$/)
{
     $error{zip} = "Invalid postal code.";
}

##</code><code>##

sub valid_ip
{
     my $bit = '[01]?\d\d?|2[0-4]\d|25[0-5]';
     return $_[0] =~ /^($bit)(\.($bit)){3}/;
}

##</code><code>##

sub valid_ip
{
        my $bits = 0;
        foreach (split (/\./, $_[0]))
        {
                return unless /^\d+$/ && $_ >= 0 && $_ < 256;
                $bits++;
        }

        return $bits == 4;
}

##</code><code>##

use Net::IPv6Addr;

sub valid_ipv6 
{
     return Net::IPv6Addr::ipv6_parse($_[0]);
}