The problem is that $dbh->dbix_threaded_start_prepare won't return the statement object handle, so $sth ends up being empty.

I agree that the documentation is very confusing.

The $dbh->dbix_threaded_start_* calls don't return handles, they return immediately with IDs.

You then have call $rc = $h->dbix_threaded_wait( $id ); to wait for the thing you started to complete.

So, to asynchonously prepare a statement, you'd do (something like; untested):

my $prepID = $dbh->dbix_threaded_start_prepare( $sql, ... );
...
## you can do other stuff here
...
my $sth = $dbh->dbix_threaded_wait($id);
[download]

But you don't need to use the asynchronous calls for everything. You could just use the normal dbi calls for some things.

Oh didn't realize that DBIx is direct subclass, so I can use all the methods of DBI. Anyway I changed the script accordingly (using just one $dbh DBIx Threaded object), and instead of the async methods I use regular ones, but now the problem is that script isn't able make use of more then one connection, so after one thread is created and detached, the second throws fatal error, as it is unable 'prepare' the statement and return $sth object...

my $dbh = DBIx::Threaded->connect("DBI:mysql:database=$database;host=$
+host", $user, $password);
DBIx::Threaded->dbix_threaded_create_pool(10);

my $sth = $dbh->prepare("SELECT id,domain,DATE(created) FROM domain_li
+st");
$sth->execute();

my $counter = 0;
 
while (my @row = $sth->fetchrow_array())
{
    my $id = $row[0];
    my $domain = $row[1];
    my $created = $row[2];
    next unless $row[0..3];
    my $thr = threads->create(mx_lookup,$id,$domain,$created,$dbh) unl
+ess $counter >= $thread_no;
    $thr->detach && $counter++ if $thr;
}
$sth->finish();

sub mx_lookup {
    my $id = shift;
    my $domain = shift;
    my $date_c = shift;
    
    my @date_c = split /-/, $date_c;
    my $delta = Delta_Days(@date_c,@date);
    my %emails_in;
    my %emails_out;
    
    if ($delta <= 30)
    {
        my @mx = mx($domain);
        #add multiple mxs support here
        my $mx_count = @mx;
         my $mx = $mx[0]->exchange;
        
        #find the last change for the given domain
        my $sth = $dbh->prepare("select max(id),domain_id,changed_from
+,changed_to,date from mx_history where domain_id=?"); #this is where 
+the script fails
        $sth->execute($id);
        
        my @row = $sth->fetchrow_array();
        $sth->finish();
    }
}
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And $dbh->errstr is -->

Thread 43 terminated abnormally: Error:Unexpected db_prepare request: 
+must be connected to do that.
[download]

seems like that the $dbh handle isn't conected at all...