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One of the most common pieces of good advice heard in the Perl discussion forums is that you shouldn't reinvent the wheel. Other folks have written code that you can put to use. The most frequent way to add to what Perl can do is by using a library or module. Many of these come with Perl, while others are available from CPAN. Of course, you can even write your own libraries and modules.
Many programming languages offer support for libraries much as Perl does. Libraries are collections of (mostly) subroutines for a given purpose. In modern Perl, though, it's more common to use modules than libraries.