I know one can increase the knowledge in a programming language - by using the "doing it" approach. What are the other means by which I can improve it?

• Get a good modern perl book and read it cover to cover. For more information on Perl books, see So what is your Perl book "Trilogy" anyway?
• Hang around Perl Monks and try to answer questions.
• Post some code you wrote to Perl Monks and ask for feedback -- so long as you are not overly sensitive to criticism, you will learn a lot from the feedback you receive here.
• Learn from how others have done it. Perl Monks Super Search turned up these relevant nodes: Re: Real Life Perl Exercises, Best ways of learning Perl!, seeking direction to start with perl