use strict;
use warnings;

use 5.10.0;

package B11 {
    use Moo;
    has b1 => (
        is      => 'rw',
        default => 'b1',
    );
}

package B21 {
    use Moo;
    has b2 => (
        is      => 'rw',
        default => 'b2',
    );
}

package C11 {
    use Moo;
    extends 'B11', 'B21';
}

my $q = C11->new;

say $q->b1;
say $q->b2;