use strict;
use warnings;

use 5.10.0;

package B1 {
    sub new { bless {}, shift }
    sub b1 { 'b1' }
}

package B2 {
    sub new { bless {}, shift }
    sub b2 { 'b2' }
}

package C1 {
    use base 'B1', 'B2';
    sub new { bless {}, shift }
}

my $q = C1->new;

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