Some interesting articles by various authors:

Testing
Re: Unit Testing and Perl Module Development
Re: Unit Testing and Perl Module Development
Regression testing with dependencies
The Joy of Test
How You (Yes You!) Can Get Involved

Benchmarking
Benchmarking Your Code

Graphing, PDF, SVG, etc
Drawing Graphs
Drawing Graphs
Drawing Graphs

Database
The fine art of database programming

Writing CPAN Modules
The fine art of database programming
Re: MakeMaker, h2xs, and writing CPAN modules
Re: MakeMaker, h2xs, and writing CPAN modules
How to make a CPAN Module Distribution
Re: Module Building and h2xs

Persistent Objects
Object Serialization Basics
Re: Persistence for options? - summary of modules for data serialization

Encryption
Encrypting Credit card numbers

File Formats
Re: Re: Best X-delimited format?

Random Numbers
Random Sampling

Misc/Unclassified
dispatch table of functions and arguments
TWAIN Issues and Perl