(1) In software, a module is a part of a program. Programs are composed of one or more independently developed modules that are not combined until the program is linked. A single module can contain one or several routines.
(2) In hardware, a module is a self-contained component.
Perl 5 module FAQ Contains a list of Perl 5 modules (reusable software). Also contains module terminology, guidelines for creation, converting Perl 4 library scripts into modules, and guidelines for reusing application code.