A vast number of techniques are used in OO software development in Perl; many more than I have space to explore in this book. For more details than can fit into this book, I recommend these sources for more details on OO programming in Perl.
Object Oriented Perl by Damian Conway (Manning Publishers). This is an excellent book and is useful for beginners to advanced. It even includes a few bioinformatics examples! My introduction to OO Perl has drawn gratefully on Conway's book. I urge readers who will be doing further OO Perl programming to get a copy. Some material is slightly dated; for example, the material on pseudohashes should be skipped.
The perlobj page from the Perl documentation.
The perlboot tutorial page from the Perl documentation is a beginning introduction to Perl objects.
The perltoot tutorial page from the Perl documentation is a more detailed introduction to Perl objects.
The perltootc tutorial page from the Perl documentation also includes more information on class methods.
The perlbot tutorial page from the Perl documentation is a bag of tricks for Perl OO programming.
Some books already mentioned in earlier chapters have extensive information about Perl OO programming, such as Programming Perl, Perl Cookbook, and Advanced Perl Programming.