my %booklist_l;
@booklist_l{ @book_id_list }
    = ( { title => 'empty', update_id => 'missing' } )
      x scalar @book_id_list;

##</code><code>##

$booklist_l{ $book_id } = $sth->fetchrow_hashref;

##</code><code>##

$booklist_l{ $book_id } = { %{$sth->fetchrow_hashref} };

##</code><code>##

foreach $book_id (keys %booklist_1) {
    my $r = $booklist_l{$book_id};
    print "XXX $book_id > $r->{'update_id'} -- from $r\n";
}