London Perl Workshop 2006

Yesterday was the London Perl Workshop, a one-day, two-track conference put together by the London Perl Mongers (in particular, muttley and Greg). I arrived early (mostly due to my lack of faith in train times), so got to put up posters first.

First talk of the day was Jesse Vincent on Jifty, the web application framework originating from within Best Practical. It was a basic introduction—making blog software, of course. Jesse took us through the details quite quickly, but it was immediately clear that very little work needs to be done for a basic CRUD app. It appears to use Mason by default, which I consider a plus point. Overall it felt very railsish, particularly the fact that it has migrations. I love migrations.

After the basic intro, he went over a few advanced features like the continuations support (of which more later) and the developer support. There’s a bunch of stuff in there that I really need to look at nicking for work, like the builtin Mason profiler support and the inline fragment editing, not to mentioned CSS::Squish and JS::Squish.

On the whole, I’m not sure about Jifty. It looks lovely, and quick to develop in. But that amount of concentrated magic scares me. I need to try out a couple of small applications to get a better feel for it.

I stayed on for the next talk, Mike Astle on wigwam (a deployment tool). I’m interested in doing deployment better, but ultimately, wigwam didn’t seem to offer that much more than what I have at the moment: a way of building packages into a compartmentalised space that can be distributed around different servers. Looking around the audience in the question time, I think I wasn’t alone.

Afterwards, I popped down to see Tom Hukins talk on “Just in time testing”. Sadly, Tom was ill. However, abigail stepped up and offered to talk about instead, highlighting the many ways in which it can be abused. He had culled a number of uses of Benchmark from perlmonks, and demonstrated various flaws. Such as not benchmarking the same thing, or trying to benchmark volatile data. The best was when he demonstrated how the compiler had completely optimised away one of the branches. Naturally executing a statement which has been optimised away is very quick.

My main beef with all of this was simply that the things being benchmarked were phenomenally simple. Really, if you care about map vs grep performance, go write it in C. Otherwise, profile your app long before you start to think about these things. demerphq pointed out that you can end up dieing the death of a thousand cuts if you don’t care about some of these little things, however.

Funnily enough, demerphq was speaking next on the changes to the regex engine coming up in Perl 5.10. This was a really deep, informative talk, and I’ll admit to glossing over some parts of it, but there were two things that really stuck out for me:

  • Recursive patterns. This makes it really easy to call back into the regex you’re matching. This is very handy for doing things like matching balanced tags correctly.
  • Named parameter groups. Nicked from .Net and Python. This should make large regexes much simpler.

Apart from that, there’s been a whole lot of work to optimize the regex engine, as well as making it properly pluggable. This now leads to the situation of making PCRE truly Perl compatible by embedding it…

After lunch, I listened to Jesse Vincent again, on “Advanced Jifty”. This was basically peeking inside some of the deep magic that’s going on in there. First, Jesse gave an overview of the message bus inside Jifty. The heart of it is IPC::PubSub. Moving on, he peeked inside Template::Declare. This is a bit like markaby. Jesse pointed out a couple of “unusual” implementation details such as local *__ANON__ = $tag; which is an undocumented way of naming auto-generated subroutines so that stack traces make sense. He also presented a quote from Audrey: “we read every bit of perlsub.pod and abused it all”.

Lastly he covered the i18n pragma, which is just filled with scary magic to make ~~'hello world' look up hello world in a message catalog and return a translated version. There’s a great deal of use of overload and overload::constant.

A this point, Jesse started to run out of time, so he rushed through a few other interesting uses of Perl:

  • Using a function called _, which is globally available in all packages.
  • Blessing into a class called 0 in order to return false from ref.
  • Creating an MD5 sum of the call stack. I’m guessing that’s how they implement continuations support.

From one mind boggling talk to another: Abigail was on next, with “Sudoku by regex”. I won’t begin to pretend to understand what it was all about, except to note that a standard 9×9 Sudoku grid took 1.5 hours to solve in a single regex. Apparently, he’s also been trying out other games in a similar fashion, except that one of them he let run for 2 weeks before pressing ^C

Alistair McGlinchy talked about “How to make a grumpy network capacity planner happy”. This was a really nice little piece on what his work as a network admin involves, and why developers chew up lots of bandwith without thinking. He gave a really good overview of HTTP caching / compression, which needs to be more widely known.

Ash Berlin spoke on Angerwhale, which is a blog that doesn’t use a database, but does use Catalyst. Consensus from my bit of the audience: why aren’t you using bloxsom? It’s smaller, simpler and works just as well.

Finally, Jos Boumans gave his superb talk on barely legal XXX Perl. It’s a detailed blow by blow account of making Acme::BadExample run, despite all the deviousness contained therein. As with Jesse’s talk, this is scary stuff, but gives a real insight into how to mold Perl to your will.

All in all, a superb day. Interesting people, interesting talks. It was well organised. I’m extremely grateful that it was put on, particularly for free thanks to the sponsors…

Anyway, after the conference, the only natural thing to do was retreat to another pub. I only spent a short while there before departing for the BBC Backstage Xmas bash

3 Comments to London Perl Workshop 2006

  1. Ash Berlin says:

    “Consensus from my bit of the audience: why aren’t you using bloxsom? It’s smaller, simpler and works just as well.”

    Cos the point of the talk (which likey wasn’t conveyed due to that being my first ever talk to more than 6 peope) was to just illustrate some points about Catalyst more than anything else

    Oh and also the markup on bloxsom makes me wince – I’m a big fan of syntactic markup, or at the very least not using tables for layout – and 404s dont help in making me want to use it

  2. I’m glad to hear that the continuations aren’t that scary. 🙂

  3. Jesse says:

    MD5ing the call stack. Actually, the continuations support is much less scary than that 😉 The MD5 trick is for a unique naming optimization to take a bit of burden off developers. (Optionally)