I would flip the data model around. One book may contain multiple chapters. They will also normally be sequentially numbered so I'd make an array of them.

#!/usr/bin/perl
use strict;
use warnings;

my %book = (
    name    => 'ABC - an adventure',
    author  => 'monk',
    isbn    => '123-890',
    issn    => '@issn',
    chapter => [],
);

$book{chapter}[1] = {
    name => 'Testing Times',
    page  => 2,
};

$book{chapter}[2] = {
    name => 'Importing Hash',
    page => 99,
};

print "$book{name}\n";

my $i = 1;
while (exists $book{chapter}[$i]) {
    print "Ch: $i '$book{chapter}[$i]{name}' ($book{chapter}[$i]{page}
+)\n";
    $i++
}
[download]

ABC - an adventure
Ch: 1 'Testing Times' (2)
Ch: 2 'Importing Hash' (99)
[download]

Cheers,
R.