use constant REGEXP_HOSTNAME      => qr/^([\w\-.]+)$/;
use constant REGEXP_IPADDR        => qr/^((?:(?:25[0-5]|2[0-4]\d|[0-1]??\d{1,2})[.](?:25[0-5]|2[0-4]\d|[0-1]??\d{1,2})[.](?:25[0-5]|2[0-4]\d|[0-1]??\d{1,2})[.](?:25[0-5]|2[0-4]\d|[0-1]??\d{1,2})))$/;

sub valid_hostname
{
   my $value = shift;

   return 0 unless $value =~ REGEXP_HOSTNAME;
   return 0 unless index($value, ".") > 0;

   my @parts = split/\./, $value;
   my $valid = @parts;

   foreach my $label (@parts)
   {
      $valid = 0 if (length $label > 63) or ($label =~ m!^\-!) or ($label =~ m!\-$!);
      last unless $valid;
   }

   $valid = 0 if $parts[-1] =~ m!^\d.*!;

   return $valid;
}

sub valid_ipaddr
{
   my $value = shift;
   return $value =~ REGEXP_IPADDR;
}

sub valid_host
{
   my $value = shift;
   return valid_hostname($value) || valid_ipaddr($value);
}