Culling My Modules

About a year ago, I dabbled briefly with Travis CI. I even gave a talk about my experiences. The plan was that I would start to use it for all of my code. But real life intervened and I never got round to getting any further with that project.

This weekend, I finally made some progress. I added a .travis.yml file to all of my Github repositories that hold CPAN modules. I even fed the details through to Coveralls so I get test coverage reports. From there it was a simple step to building a dashboard that monitors the health of all of my CPAN modules.

And it’s not a pretty picture. You’ll see a lot of grey boxes on that page, indicating that Travis couldn’t run the tests or, worse, red boxes showing that the tests failed for some reason.

Yesterday I made a few quick fixes to some of the modules (particularly in the WWW::Shorten namespace) and a couple more of them now work. But I want to work out how much effort it’s worth investing in the ones that are still failing. And, widening my scope a little, I’ve decided to take a close look at my CPAN modules and work out which ones are worth keeping and which ones I should just delete.

For example, twelve years ago I was really excited about the idea of AudioFile::Info. Most people were ripping music to MP3s, but I wasn’t following the crowd and was using Ogg Vorbis instead. AudioFile::Info and its friends was an attempt to make it easy to extract information from audio files no matter which format they were it. I suppose it was a kind of DBI for ID3 tags. But twelve years on, does anyone really care about that any more? I switched all of my music collection to MP3 years ago. If I recall correctly, the AudioFile::Info modules use a convoluted hand-crafted plugin system which never worked as well as it should. I could probably switch them to use some kind of plugin architecture from CPAN. But is it worth the effort?

Then there is Guardian::OpenPlatform::API – a Perl wrapper around the Guardian’s API. I believe they changed the API end-point several years ago so the module doesn’t even work. But the fact that I’ve had no complaints about that, probably indicates that no-one has ever used it.

It’s a similar story for Net::Backpack. To be honest, I have no idea whether or not it still works. Is Backpack still running? Ok, I’ve just checked and they’re no longer offering it to new customers. But if I’m not a paying customer is there any way I can test that it still works?

Finally, there is the WWW::Shorten family of modules. I released a module called WWW::MakeAShorterLink back in 2002, but it was Iain Truskett who realised that there should be a family of modules around the (at the time new) URL-shortening industry. I took over the module when Iain passed away and I’ve been maintaining it ever since. But it’s a real pain to maintain. The URL-shortening industry changes really quickly. For a long time, new services were popping up all of the time (and many of them closed down just as quickly). I haven’t been anywhere near quick enough at releasing versions that keep up with all the changes. I suspect that at least a couple of the current test failures are down to services that have closed down. I should probably investigate those over the next few days.

I don’t think WWW::Shorten is in any danger of going away (but I need to find a better way to keep abreast of changes in the industry) but the other modules I’ve mentioned here (AudioFile::Info::*, Guardian::OpenPlatform::API and Net::Backpack) are on borrowed time. If you’re using them and you’d like to see new versions of them in the future then let me know. If you’d like to take over maintenance, then that would be even better.

If I don’t hear from anyone (and I strongly suspect that I won’t) then I’ll be removing them from CPAN in a couple of months time.

Mailing Lists

Over the years I’ve set up a few mailing lists for the discussion of various projects I’ve been involved with. There’s always an expectation that mailing lists will flourish without much input from me. But it never works out like that.

The truth is that most mailing lists just quietly die. And, in many cases, they end up attracting a lot of spam – which the owner of the list has to check on a semi-regular basis on the off-chance that there’s something interesting or useful in amongst the crap. There never is.

So I’ve decided to close a few mailing lists that didn’t seem to be going anywhere. I don’t suppose anyone will miss them, but I’ve taken a copy of the archives and I may do something with them at some point in the future.

The lists that I have removed are:

  • perlanet@perlhacks.com
  • perl-api-squad@perlhacks.com
  • perl-mooc@perlhacks.com
  • training-news@learnperl.co.uk
  • xml-feed@perlhacks.com

A couple of these lists have received slightly special treatment. The xml-feed list is advertised as the support email address for XML::Feed. I’ve redirected that address so that mail now comes to me. Hopefully my spam filters will ensure that I’m not overrun with spam from it before I work out a more permanent solution.

The other list that has been treated differently is the training-news one. That was set up so that people could get information about upcoming training courses that I would be running. I still think that’s useful, so I’ve replaced it with a new list (run by MailChimp). If you’re interested in keeping in touch with what I’m doing then please sign up to the new list by entering your email address below. (The same form will now appear in the sidebar on every page of this site.)


Sign up here for occasional email about stuff I'm doing with Perl, information about upcoming talks and training courses and other updates.

(I promise not to spam you.)


So, there you are. I’ve removed a few moribund mailing lists. I hope that hasn’t ruined anyone’s day.

Building TwittElection

I was asked to write a guest post for the Built In Perl blog. I wrote something about how I built my site, TwittElection, for the recent UK general election.

In the UK we have just had a general election. Over the last few weeks many web sites have sprung up to share information about the campaign and to help people decide how to vote. I have set up my own site called TwittElection and in this article I’d like to explain a little about how it works.

But why not go over to Built In Perl and read the whole thing there.

Incidentally, on 13th June, I’ll be giving a talk about TwittElection at this year’s OpenTech conference. If you’re interested in the positive impact that technology can have on society then you’ll, no doubt, find OpenTech very interesting.

DBIC Training in Granada

It’s been a while since I’ve run a training course alongside a YAPC. By my calculations, the last time was Riga in 2011. But I’ve been talking to the organisers of this year’s conference and we have plan.

I’m going to be running a one-day introductory course on DBIx::Class before the conference (I think it’ll be on 1st September, but that’s not 100% certain yet). Full details are on the conference web site. There’s an early-bird price of 150 Euro and the full price is 200 Euro. The web site says that the early-bird price finishes today, but I wouldn’t be at all surprised if that gets extended for a few days at least.

Of course, readers of this blog will all already be experts in DBIC and won’t need this course. But I’m sure that most of you will have a colleague who would benefit from… well… a refresher on who DBIC works. Why not see if your company will pay for them to attend the course :-)

The course size is limited. So you might want to think about booking soon.

Hope to see some of you in Granada.

Two updates:

  1. The date has now been confirmed as 1st September.
  2. The early-bird pricing has been extended until 1st June.

Subroutines and Ampersands

I’ve had this discussion several times recently, so I thought it was worth writing a blog post so that I have somewhere to point people the next time it comes up.

Using ampersands on subroutine calls (&my_sub or &my_sub(...)) is never necessary and can have potentially surprising side-effects. It should, therefore, never be used and should particularly be avoided in examples aimed at beginners.

Using an ampersand when calling a subroutine has three effects.

  1. It disambiguates the code so the the Perl compiler knows for sure that it has come across a subroutine call.
  2. It turns off prototype checking.
  3. If you use the &my_sub form (i.e. without parentheses) then the current value of @_ is passed on to the called subroutine.

Let’s look at these three effects in a little more detail.

Disambiguating the code is obviously a good idea. But adding the ampersand is not the only way to do it. Adding a pair of parentheses to the end of the call (my_sub()) has exactly the same effect. And, as a bonus, it looks the same as subroutine calls do in pretty much every other programming language ever invented. I can’t think of a single reason why anyone would pick &my_sub over my_sub().

I hope we’re agreed that prototypes are unnecessary in most Perl code (perhaps that needs to be another blog post at some point). Of course there are a few good reasons to use them, but most of us won’t be using them most of the time. If you’re using them, then turning off prototype checking seems to be a bad idea. And if you’re not using them, then it doesn’t matter whether they’re checked or not. There’s no good argument here for  using ampersands.

Then we come to the invisible passing of @_ to the called subroutine. I have no idea why anyone ever thought this was a good idea. The perlsub documentation calls it “an efficiency mechanism” but admits that is it one “that new users may wish to avoid”. If you want @_ to be available to the called subroutine then just pass it in explicitly. Your maintenance programmer (and remember, that could be you in six months time) will be grateful and won’t waste hours trying to work out what is going on.

So, no, there is no good reason to use ampersands when calling subroutines. Please don’t use them.

There is, of course, one case where ampersands are still useful when dealing with subroutines – when you are taking a reference to an existing, named subroutine. But that’s the only case that I can think of.

What do you think? Have I missed something?

It’s unfortunate that a lot of the older documentation on CPAN (and, indeed, some popular beginners’ books) still perpetuate this outdated style. It would be great if we could remove it from all example code.

Modern Perl Articles

Back in 2011 I wrote a series of three articles about “Modern Perl” for Linux Format. Although I mentioned all three articles here as they were published, I didn’t post the actual contents of the articles as I wasn’t sure about the copyright situation.

But now I suspect that enough time has passed that copyright is no longer going to be an issue, so I’ve added the full text of the articles to this site. The articles are all about writing a simple web application to track your reading. They use DBIx::Class and Dancer.

Let me know if you find them interesting or useful.

Penetration Testing with Perl

I was sent a review copy of Penetration Testing with Perl by Douglas Berdeaux. I really didn’t like it. Here’s the review I’ve been sharing on Amazon and Goodreads.

I’ve been wanting to learn a bit about Penetration Testing for a while and as Perl is my programming language of choice this seemed like a great book to choose. Unfortunately, it wasn’t.

I have no doubt that the author knows what he is talking about when it comes to Penetration Testing, but there were several things that prevented this book from transferring much of that knowledge to me.

Firstly, the typesetting in the book is terrible. I was reading the Amazon eBook edition – it’s possible that the printed version is better. For example, there’s a lot of code in this book and it’s in a proportional font. In order for code to be readable, it needs to be in a fixed-width font. Also, there are two or three places where an equation appears in the text, but it appears in an unreadably small font. I have just checked in the PDF version of the book and neither of these problems appear there. It would seem that this is down to a problem in Packt’s eBook creation process.

Secondly, it’s obvious that English is not the author’s first language. At times this really prevents him from getting his point across clearly. I’m very happy to see non-native speakers publishing books in English. But the publishers need to provide high quality proof-readers to ensure that the language is good enough.

Thirdly, the organisation of the book is a little haphazard. The first couple of chapters are introductions to Perl and Linux, but after that we are dropped immediately into a discussion of network sniffing. Later in the book there are chapters on intelligence gathering, social engineering and password cracking. These are all far simpler topics which could have served as a gentle introduction to the book, getting people up to speed on Perl before delving into the complex internals of network packets. Once again, I think this should be the responsibility of the publisher. There should be a good editor working on the book alongside the author and shaping the manuscript so that the story it tells guides the user through the subject as easily as possible.

Finally, the book falls short in its technical content. I can’t comment on the author’s explanations of Penetration Testing (I was, after all, reading the book to learn about that topic), but the Perl code that he uses throughout the book is really bad. He is obviously someone who only ever learned enough Perl to get his job done and never bothered to learn how Perl really works or to keep his knowledge up to date. As a result, the book is full of the kind of code that gives Perl its reputation as a write-only language. The idioms that he uses are often out of date (using ‘-w’ instead of ‘use warnings’, for example), confusing (predeclaring subroutines unnecessarily, using ampersands on function calls) or just plain wrong (‘my ($x, $y, $z) = 0 x 3′ just doesn’t do what he thinks it does). Actually, it’s worse than that. It’s not just Perl he doesn’t understand, it’s the fundamentals of good software engineering. His code is a confusing mess of global variables and bad design. This is another failure by the publisher. There should have been a competent technical editor checking this stuff.

I’ve read four or five Packt books now. They’re all of this standard. None of them should have been published. But Packt seem to have hit on a good business model. They find unknown authors and produce books as cheaply as possible. Their publishing process omits all of the editing and checking that more reputable publishers use. The books that come out of this process are, of course, terrible. But, for reasons I can’t understand, people still buy them.

Packt books – just say no.

London Perl Jobs Mailing List

London.pm is undergoing one of its periodic reorganisations. We’re in the process of moving our web site over to a new server and as part of that move, we’ve decided that we’ll move our mailing list infrastructure to a third party system. Both the main discussion list and the announcements list will be run on Sympa.

But that’s not all the lists we currently have. In particular, we had a London Perl Jobs list, which anyone could use to post details of Perl jobs in London. It’s been decided that this list is too much hassle to keep up. Apparently, it needs a pretty high level of work from moderators. So that list isn’t going to be migrated and it will quietly die.

I thought that was a bit of a shame. I think it’s a useful list. And, in particular, I think it would be easy for outsiders to misread the reasons for the closure – given the current discussions about the death of Perl. Perhaps the list was killed off because there are no longer any Perl jobs in London (you and I both know that’s not true, but not everyone is following the situation as closely as we are).

So I decided to do something about it. I just happened to have a useful-looking domain sitting around not doing very much, so I’ve set up a jobs mailing list over there. Feel free to subscribe if you’re interested in Perl jobs in London. And, more importantly, please encourage people who are looking for Perl programmers in London to post their jobs to jobs@londonperl.co.uk.

Currently, the list is configured like this:

  • Archives are public
  • By default, replies go to the poster rather than the list
  • Posts are accepted from anyone
  • All posts are moderated

I’ll be happy to reconsider any of those settings once the list has been running for a while. I’m also considering setting up an associated jobs discussion list, if people think that would be useful.

See you on the mailing list.

Slideshare Stats

For many years (since the end of 2007, apparently) I’ve been uploading the slides from my talks and training courses to Slideshare.

This morning I got an email from them, telling me that they had made their analytics pages freely available. I don’t know if this is a permanent change or a special offer, but the link (which will only work for logged in users) is http://www.slideshare.net/insight.

There’s a lot of information there and I look forward into digging into it in a lot more detail. But I thought it would be interesting to share the list of my top ten most popular slide decks.

Title Views
Introduction to Perl – Day 1 71722
LPW: Beginners Perl 50935
Modern Web Development with Perl 33034
Modern Perl for Non-Perl Programmers 27376
Matt’s PSGI Archive 24341
Introduction to Web Programming with Perl 22544
Introduction to Perl – Day 2 20489
Introduction to Modern Perl 17709
Introducing Modern Perl 13871
Modern Core Perl 11337

A lot of those course are aimed at people who are starting Perl from scratch. I guess it’s true that there are plenty of people out there who still want to learn Perl.

Dev Assistant

A couple of days ago, I updated to my laptop to Fedora 21. One of the new features was an application called DevAssistant which claimed that:

It does not matter if you only recently discovered the world of software development, or if you have been coding for two decades, there’s always something DevAssistant can do to make your life easier.

I thought it was worth investigating – particularly when I saw that it had support for Perl.

Starting the GUI and pressing the Perl button gives me two options: “Basic Class” and “Dancer”. I chose the “Basic Class” option. That gave me an dialogue box where I could give my new project a name. I chose “MyClass” (it’s only an example!) This created a directory called MyClass in my home directory and put two files in that directory. Here are the contents of those two files.

main.pl

myClass.pm

It’s great, of course, that the project wants to support Perl. I think that we should do everything we can to help them. But it’s clear to me that they don’t have anyone on the team who knows anything about modern Perl practices.

So who wants to volunteer to help them?

Update: So it turns out that the dev team are really responsive to pull requests :-)