if ($response->is_success()) {
    for my $prop ($response->properties) {
        my %info;
        $info{'title'}        = $prop->title();
        $info{'authors'}      = join(", ",$prop->authors());
        $info{'isbn'}         = $prop->isbn();
        $info{'pages'}        = $prop->numpages();
        $info{'publisher'}    = $prop->publisher();
        $info{'image_small'}  = $prop->ImageUrlSmall();
        $info{'image_medium'} = $prop->ImageUrlMedium();

        push $books{$prop->publication_date()}, \%info;
    }
    print Dumper \%books;
}