Programmer Musings

Review of Perl Best Practices

Perl Best Practices
Damian Conway
O'Reilly, 2005

This book is hard to summarize. There is much good advice in this book. Unfortunately, there's also some advice that I found questionable. Conway covers some of important Perl programming and general programming best practices, including consistent formatting, use of strict and warnings, and the use of version control software. Unlike my standard book on best practices, Code Complete, Conway does not provide much independent support for his assertions. On the obvious best practices (meaning those you agree with), this is not a big issue. However, I did find it difficult to accept suggestions to change coding practices I've developed over almost two decades without any supporting evidence.

Without that evidence, I found some of Conway's arguments to be less than convincing. For example at the beginning of Chapter 2, he states that consistent layout is important, but which particular layout style you use does not matter at all. So far I agree with him completely. Then, he goes on to spend over 25 pages describing his preferred layout style, listing each point as a best practice and spending time justifying his choices. If the particular layout style does not matter, shouldn't we have had one best practice, use a consistent layout style instead of 22 individual layout suggestions elevated to best practice status?

I was also interested to find that more than 10 of the recommended modules were written by Damian Conway. Some of these appear to have been updated on CPAN relatively recently. That makes me wonder how they have had time to become best practice.

Some of his rules appeared to be somewhat contradictory. For instance, we shouldn't use unless because it is not as familiar to many programmers and it is harder to understand complicated boolean expressions in an unless. But, we should use redo to restart a for loop without incrementing the variable when we need more complex flow control. And we should prefer \A and \z in regular expressions, because

They're likely to be unfamiliar to the readers of your code, in which case those readers will have to look them up, rather than blithely misunderstanding them.

Although these suggestions may be good practice and may actually help in writing maintainable code, I find it impossible to detect an underlying philosophy driving this particular set of suggestions.

If you've read this far, you probably have gotten the impression that I hated this book. That is very far from the truth. Damian Conway is a prolific Perl programmer with loads of experience. Much of his advice parallels my own philosophy in writing code, in Perl and in other languages. As I was reading the book, I installed several of his suggested modules and have even modified a few of my Perl programming practices based on his arguments. However, I would be uncomfortable suggesting that a new Perl programmer use this book as the reference on how to program in Perl.

In general, I believe that my biggest problem stems from the expectations I had from the title. If it had been called Damian Conway's Recommended Practices for Perl, I would have been a bit more forgiving. However, by setting itself up as the book on Perl best practices, I feel that the practices in the book need to be more than Conway's recommendations. Supporting evidence or studies would have made it easier to swallow his suggestions where they disagreed with my own practice. Less inconsistency between different rules would have made me more comfortable that he has an underlying strategy instead of listing the part of the language that he, personally, likes. Better disclosure about the modules he wrote and their age, would have made the book feel less like an infomercial in spots.

All in all, I think I would recommend this book to more senior Perl programmers or senior programmers coming to Perl. I would be a little leary of recommending it to novice Perl programmers without some strong suggestions that they take this as one person's view. The really frustrating thing is that I really wanted a book to be the standard I could use to counteract the myth of write-only Perl. Unfortunately, I don't think this book will do that.

All that being said, there is a large amount of good advice in this book. As long as you take the advice with an appropriately-sized grain of salt, this book could improve your Perl code.