constraints => {
     image_name => [
     {
         constraint_method => 'file_format',
     },
     {
         constraint_method => 'file_max_bytes',
         params => [\100],
     },
     {
         constraint_method => 'image_max_dimensions',
         params => [\200,\200],
     },
 
     ],

##</code><code>##

     foo => { constraint_method => 'bar', params => \@args },

##</code><code>##

     foo => { constraint => 'bar', params => [$dfv, @args]] },

##</code><code>##

     foo => { constraint => 'bar', params => [$dfv, 'foo', @args] },

##</code><code>##

bar($dfv, @args);
$dfv->bar(@args);