mysql> show create table t1 ;
+-------+--------------------------------------------+
| Table | Create Table                                                                                                                 |
+-------+--------------------------------------------+
| t1    | CREATE TABLE `t1` (
  `a` varchar(100) default 'TEST TABLE',
  `b` int(11) default '10'
) ENGINE=MyISAM DEFAULT CHARSET=utf8 |
+-------+-------------------------------------------+

##</code><code>##

#! /usr/bin/perl

use DBI;
use strict ;

my $dsn = "DBI:mysql:database=test;host=localhost";
my $dbh = DBI->connect($dsn, "root", "");

my $sth = $dbh->prepare("INSERT INTO t1 (a,b) VALUES(?,?)") ;

my @a = (undef,undef ) ;
$sth->execute(@a) ;

$dbh->disconnect() ;

##</code><code>##

mysql> select * from t1 ;
+------+------+
| a    | b    |
+------+------+
|      | NULL |
+------+------+
1 row in set (0.00 sec)