Apache2 filter

Hi.

I am trying to write an Apache2 request filter.
According to the online tutorial 
(http://perl.apache.org/docs/2.0/user/handlers/filters.html#Output_Filters). I have this 
so far :

package MyFilter;
...
use base qw(Apache2::Filter);
...
use constant BUFF_LEN => 4096;

sub handler : FilterRequestHandler {
	my $f = shift;
	my $content = '';

	while ($f->read(my $buffer, BUFF_LEN)) {
		$content .= $buffer;
	}
}

  but when I compile this :

aw@arthur:~/tests$ perl -cw PAGELINKS.pm
Invalid CODE attribute: FilterRequestHandler at PAGELINKS.pm line 50.
BEGIN failed--compilation aborted at PAGELINKS.pm line 50.
aw@arthur:~/tests$

platform data (from Apache log) :
[Tue Sep 01 06:25:10 2015] [notice] Apache/2.2.16 (Debian) DAV/2 SVN/1.6.12 mod_jk/1.2.30 
mod_apreq2-20090110/2.7.1 mod_perl/2.0.4 Perl/v5.10.1 configured -- resuming normal operations

There are already many other mod_perl modules of all kinds running on that same server 
(but not filters).

What I am missing ?

André