Doesn't answer your question, but as an alternate method... store the filename of the book contents instead of the actual contents as in:

$books = {
  "Moby Dick" => '/path/to/books/moby_dick.dat',
  "LoTR"      => '/path/to/books/lotr.dat',
};
[download]

my @a=qw(random brilliant braindead); print $a[rand(@a)];