package MyApacheHandler;

use base 'HTML::Mason::ApacheHandler';

sub prepare_request {
  my $self = shift;  
  my $r     = shift;

  my $post_max = 100; 

 Apache::Request->instance( $r, POST_MAX => $post_max );

 return $self->SUPER::prepare_request( $r, @_ );
}
  
1;

##</code><code>##

<%init>
use MyApacheHandler;

my $apr    = MyApacheHandler::prepare_request($r,POST_MAX => 1);
</%init>