ProductVariant.pm

package Role::DBH;
...


has _config => (
    isa     => 'Config::Merge',
    is      => 'ro'
    lazy    => 1,
    default => sub { Config::Merge->new('/path/to/config'); },
);

has _dbh => (
    isa => 'DBI::db',
    is  => 'ro',
    lazy => 1,
    default => sub { my $self = shift;
        DBI->connect( $self->_config->('db.dsn'), $self->_config->('db.user'), $self->_config->('db.pass') );
    },
);

package ProductVariant;
with 'Role::DBH';

sub _load_categories {
...
     $self->_dbh
}