The Perl community on LinkedIn is fascinating. It’s a great way to see how Perl is perceived and used outside of the echo chamber. And that’s a real eye-opener.
Here’s an example. Every few weeks (it seems) someone asks for advice on Perl books.At that point a few people will jump in with sensible suggestions. But for every reasonable suggestion, you’ll get three or four people suggesting something from this list:
- Something horribly out of date. A lot of publishers stopped updating their Perl books about ten years ago. The most recent version of Perl Black Book that I can find is from 2001. Teach Yourself Perl in 21 Days was last updated in 2002. Perl By Example dates from 2007. I haven’t read any of these books, so I can’t comment on their quality, but I’d be really wary of suggesting that someone learns Perl from a book that is so out of date. Before the days of Amazon, these books would quietly disappear from bookshops, but now they always seem to be available.
- Something out of date, but that used to be great. There are plenty of books that I would have recommended when they were current, but that I wouldn’t really want to recommend now. A lot of these are O’Reilly books that haven’t been updated recently – Advanced Perl Programming and The Perl Cookbook, for example. I’m sure there’s lots of good stuff in those books. But I really wouldn’t want anyone to read them if they didn’t already have enough experience to update the Perl to current best practices. I sometimes recommend these books myself, but only in specific circumstances. Whenever I run a course on OO Perl I mention Damian’s book. But I also point out that there have been a lot of advances in the area since the book was published. And, I have to confess, my own Data Munging with Perl fits firmly in this category.
- Something of dubious provenance. Most of these discussions will, at some point, attract a link to some dubious web site in Eastern Europe that contains the full text of O’Reilly’s various CD bookshelves. I know that these sites exist and I know that there’s nothing that O’Reilly can do about them, But I’d rather not see them mentioned on a professional site like LinkedIn. And quite apart from the copyright issues, there’s the fact that most of the books on these sites fall firmly into the first category above. They’re all over ten years old.
- Some great tutorial on the internet. I’ve talked about the problems of old and dodgy tutorials before. And things definitely seem to be looking up. We are getting more good tutorials out there. But people still insist on sharing links to the tutorial that they learned from. Even if it’s appalling.
In a recent discussion someone said (and I’m paraphrasing) “just go to Amazon and look for the highest rated books”. I think there are two problems with that:
- The people who are rating beginner’s programming books on Amazon are usually the least qualified people to do that. Sure, they can tell how easy the book was to read and how well they picked up what the author taught them. But they have noway of knowing whether what they learned was accurate or useful.
- Amazon ratings last forever. But, as noted above, the quality of a technical book in fast-moving subject like programming falls over time. Perhaps Amazon ratings on programming books should have a half-life.
Here are some examples of things that you’re going to miss out on by using outdated Perl references.
- say – We all love say, don’t we?
- Lexical filehandles – Storing filehandles in lexical variables is great. I no longer have to worry about bareword filehandles being reused elsewhere in the code.
- Defined or operator – There’s now no excuse for the $val ||= $default bug.
- given/when – Perl has a switch statement. And it’s better than anyone else’s 🙂
- Unicode support – Perl’s Unicode support is second to none. Except, if you’re using an old version of Perl in which case it’s a bit rubbish. And if you’re reading about Perl in an old book, then you won’t know about it.
- State variables – Ok, I don’t use those every day. But when I need them, they make my code cleaner.
And then there are all the great CPAN modules that aren’t covered in books that were written before they were released. Would you really want to introduce someone to OO Perl without mentioning Moose?
My rules for recommending books are pretty simple. They should be books that I’ve found useful and they should have been published in the last few years. And given the falling numbers of Perl books that are published each year, that’s now a rather small number of books. Perhaps a dozen or so.
Am I being too harsh? Can beginners get something useful out of older Perl books? How do you decide whether to recommend a book to a colleague?