trying to subclass DBI

Hi,

I'm new to OO programming, and i'd like to subclass DBI for some purpose.

I made some tests to figure out how it worked. Here is a sample code
that doesn't do anything interesting. It doesn't execute as I
expected:

======================
package MySubDBI;

use strict;

use DBI;
use vars qw(@ISA);
@ISA = qw(DBI);

package MySubDBI::db;
use vars qw(@ISA);
@ISA = qw(DBI::db);

sub connect {
my ($drh, @args) = @_;
my $dbh = $drh->SUPER::connect(@args) or return;
$dbh->{private_mysubdbi_test} = 'blabla';
print "test0\n";
return $dbh;
}

sub test {
my $dbh = shift;
return $dbh->{private_mysubdbi_test};
}

package MySubDBI::st;
use vars qw(@ISA);
@ISA = qw(DBI::st);

package Main;

my $dbn = "DBI:mysql:database=***:host=***:port=***";

my $dbh = MySubDBI->connect( $dbn, '***', '***' );
if ( $dbh ) { print "connection ok\n" } else { print "connection error\n" }

print 'test1: ', $dbh->{private_mysubdbi_test}, "\n";
print 'test2: ', $dbh->test, "\n";
======================

It prints:
connection ok
test1:
test2:

Do you know why it doesn't print the string 'test0' and nothing for
test1 and test2 ?
.

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