package myApp::View::TT;

 use strict;
 use base 'Catalyst::View::TT';

 __PACKAGE__->config({
   CATALYST_VAR => 'catalyst',
   ...
   FILTERS => {
     yesno => sub { $_[0] ? 'yes' : 'no'; },
     onoff => sub { $_[0] ? 'on' : 'off'; },
   },
 });