Perlhandler bugs when set up on the root of the domain

Hi everyone,

i've start working with mod_perl and perlhandler few weeks ago in a 
folder of my domain (mydomain.com/folder/) and everything was fine.

I've recently tried to set it up on the root of my domain, but now, i've 
got an error 500 when i try to go to mydomain.com and the logs says :

  Can't locate object method "content_type" via package 
"Apache2::RequestRec" at /usr/lib/perl5/...

And if i add use Apache2::RequestRec after my package definition the 
error change from content_type to print.
The test code is really simple :
package test2::Rules2;
use Apache2::Const qw(:common);

sub handler {
my $r = shift;
$r->content_type("text/plain");
$r->print("mod_perl rules!\n");
return OK;
}
1;

Any idea on where it comes from?

Thanks
David