#only there for the validator below which do stuff after build.
sub BUILD {}
 
has '_creative_validators' => (
    is      => 'ro',
    default => sub { [] },
);

sub register_validator {
    my ($class, $sub) = @_;
    $class->can('after')->(BUILD => sub {
        my ($self) = @_;
        push @{$self->_creative_validators}, $sub;
    });  
}  

##</code><code>##

use Moo::Role;
with 'Weborama::Collect::CreativesValidator';

#you have to define that one
requires qw/creatives_validator_publisher_forced_pause_settings/;
 
__PACKAGE__->register_validator(sub {
    my ( $self, @creatives ) = @_;
    ...
})