You don't need a different module for each group (Well, "module" is a very loose definition, so what follows you may consider different modules. But it's all can be one file):

package Whatever;  # Really, whatever. Can even omit this line.
use strict;
use warnings;
#
# Chapters go here
#
$Chapter::one = 'Chapter 1';
$Chapter::two = 'Chapter 2';
#
# Authors go here
#
$Author::LW = 'Larry Wall';
$Author::KV = 'Kurt Vonnegut';
#
# References go here
#
$Reference::foo = 'Over there -->';
$Reference::bar = 'Switch doors!';
$Reference::baz = 'Yesteryear';
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