Perl, Randal L. Schwartz, Brian D Foy, Tom Phoenix 

This book picks up right where Learning Perl leaves off. With Intermediate Perl, you’ll graduate from short scripts to much larger programs, using features that make Perl a general-purpose language. This gentle but thorough guide introduces you to modules, complex data structures, and object-oriented programming.

Each chapter is small enough to be read in just an hour or two, ending with exercises to help you practice what you’ve learned. If you’re familiar with the material in Learning Perl and have the ambition to go further, Intermediate Perl will teach you most of the core Perl language concepts you need for writing robust programs on any platform.

Topics include:

Packages and namespaces
References and scoping, including regular expression references
Manipulating complex data structures
Object-oriented programming
Writing and using modules
Testing Perl code
Contributing to CPAN
Just like Learning Perl, material in this book closely follows the popular introductory Perl course the authors have taught since 1991. This second edition covers recent changes to the language up to version 5.14.