I think the bug is here. Try to write something like 
while ( ($book_id) = $sth->fetchrow_array() ) {
    $booklist_1{$book_id} = 1;
}

[download]
(note the extra parenthesis in order to enforce list context)

or

while ( $book_id = $sth->fetchrow_arrayref() ) {
    $booklist_1{ $book_id->[0] } = 1;
}

[download]

Code is not tested

Best regards

UPDATE:. I have overseen the kyle suggestion. It seems that the right code regarding the second loop will be: 

while ( ($book_id) = $sth->fetchrow_array() ) {
    $booklist_1{$book_id} = {};
}

[download]

In reply to Re^3: Why is my code assigning the last-retrieved value to all elements in my hash? by karavelov
in thread Why is my code assigning the last-retrieved value to all elements in my hash? by punch_card_don

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