package Super1;
package Super2;
package Sub;

@Sub::ISA = qw( Super1 Super2 );

package main;

my $sub_class = bless {}, 'Sub';
foreach my $class ( qw( Sub Super1 Super2 HASH ) ) {
    ok( $sub_class->isa( $class ), "\$sub_class->isa( '$class' )" );
}