It’s been over six weeks since I wrote my blog post on Perl usage. I really didn’t mean to leave it so long to write the follow-up. But real life intervened and I haven’t had time for much blogging. That’s still the case (I should be writing a talk right now) but I thought it was worth jotting down some quick notes about what I think is causing Perl’s decline.
We have a lot to thank Matt Wright for. And I don’t mean that sarcastically. A lot of the popularity of Perl in the mid-90s stems directly from people like Matt and Selena Sol making their collections of CGI programs available really early on. The popularity of their programs made Perl the de-facto standard for CGI programming.
But that was a double-edged sword. People searching the web for examples of CGI programming found Matt or Selena’s code and assumed they represented best practice. Which, of course, they didn’t. While people were blithely copying Matt’s programming style, good Perl programmers were using CGI.pm to parse their incoming parameters and separating their HTML generation out into templates.
In my previous post, I mentioned that fifteen or twenty years ago Perl was the programming language of choice for internet start-ups. That’s true, but a lot of the code written at that time was in the Matt Wright style. Matt’s style just about works for a guestbook or a form mailer. But when you try to build a business on top of code like that, it quickly becomes obvious that it’s an unmaintainable mess.
Many of the technical architects and CTOs who are making decisions about technology in companies today are the programmers who spent too many late nights battling those balls of mud in the 1990s. They were never really Perl programmers, they were only using it because it was fashionable, and they haven’t been keeping up with recent advances in Perl so it’s not surprising that they often choose to avoid using Perl.
A lot of Perl’s reputation as executable line noise is completely unwarranted. The people who were writing those 1990s balls of mud were under such pressure to deliver that they would have almost certainly delivered something just as unmaintainable whatever language they were using. But some of that reputation is fair. I’ve been teaching Perl for almost fifteen years and I know that there are some parts of Perl that people find confusing. Here are some examples:
Sigils – I can explain things like @array, $array[$key] and even @array[@keys] to people. And most of them get it. But it takes them a while. And then it all goes to pieces again when I have to explain the difference between $array[$key] and $array->[$key].
Context – Does any other programming language have the concept of context? Yes, when used correctly it’s a powerful tool. But it’s hard to explain and a good source of hard-to-find bugs. Can anyone honestly say that they haven’t been bitten by a context bug at some point in the last years?
Data Structures – Is the difference between arrays and array references really necessary? Think of all the complexity that is added because you can’t just pass arrays and hashes into subroutines without being bitten by list flattening. As experienced Perl programmers we know the problems and our brains are hard-wired to work around it. But other languages treat all aggregate data structures as references and it all becomes a lot easier.
I know that each of these features (and half a dozen other examples I could list) makes Perl a richer and more expressive language. But this comes at the cost of learnability and readability. Perhaps that trade-off once seemed like a good idea. When you’re trying to encourage people to look at your language then the advantages seem less obvious.
Of course, none of these features can be changed as they would break pretty much every existing Perl codebase. Which would be a terrible idea. But you can get away with a lot more breakage when you increase your major version number. Which Perl hasn’t been able to do for fourteen years.
I need to be clear here. I think that Perl 6 looks like a great language. I am really looking forward to using on production systems. And it looks like the current Perl 6 team are doing great work towards making that possible. In fact I think that our best approach to reviving Perl’s fortunes is to get a production-ready version of Perl 6 out and to make a big noise about that.
However, that name has been a big problem.
Looking from outside the Perl echo chamber, it’s easy to believe that Perl hasn’t had a major release for twenty years. And that can probably explain a lot of Perl’s current problems.
I know that people who believe that are wrong. The current version of Perl (5.20.1 as I write this) is a lot different to the version that was current when Perl 6 was first announced (which was 5.6.0, I think). Perl has gone through huge changes in the last fourteen years. But the version number hides that.
I also know that we no longer tell people that Perl 6 is the next version of Perl. The Wikipedia page makes it clear in its first sentence that “Perl 6 is a member of the Perl family of programming languages“. So why do people continue to think it’s the next version of Perl? Well, probably because people assume that they know how software version numbers work and don’t bother to check the web site to see it a particular project has changed the standard meaning that has worked well for decades.
So Perl 6 has been simultaneously both good and bad for Perl. Good because a lot of Perl 6 ideas have been backported into Perl 5. But bad because Perl 5 has been unable to change its major version number in order to advertise these improvements to the wider software-using world.
Nothing can be done about this now. The damage is done. As I said at the start of this section, it’s likely that the only thing we can do is to bet heavily on Perl 6 and get it out as soon as possible. Perl 5 will continue to exist. People will continue to maintain and improve it. Some companies will continue to use it. But it’s usage will continue to fall. I really think it’s too late to do anything about that.