Acme::OneHundredNotOut - A raise of the bat, a tip of the hat


I have just released my 100th module to CPAN, the first time that anyone has reached that target. As some of you may know, I am getting ready to go back to college and reinvent myself from being a programmer into being a missionary. I don't forsee that many more Perl modules coming out of this.

Of course, this doesn't mean that I'm going to abjure usage of Perl forever; any time there's a computer and something I need automated, out will come the Swiss Army Chainsaw and the job will get done. In fact, we recently needed to manipulate some text from a mission handbook to translate it into Japanese, and Perl was there handling and collating all that.

But 100 modules is a convenient place to stop and take stock, and I hope that those of you who have benefitted from my modules, programs or writing about Perl will forgive me a certain spot of self-indulgence as I look back over my CPAN career, especially since I feel that the diversity of modules that I've produced is a good indication of the diversity of what can be done with Perl.

Let's begin, then, with some humble beginnings, and then catch up on recent history.

The Embarrassing Past

Contrary to popular belief, I was not always a CPAN author. I started writing modules in 1998, immediately after reading the first edition of the Perl Cookbook - yes, you can blame Nat and Tom for all this. The first module that I released was Tie::DiscoveryHash, since I'd just learnt about tied hashes. As with many of my modules, it was an integral part of another software project which I actually never finished, and now can't find.

The first module that I ever wrote (but, by a curious quirk of fate, precisely the fiftieth module I released) was called String::Tokeniser, which is still a reasonably handy way of getting an iterator over tokenising a string. (Someone recently released String::Tokenizer, which makes me laugh.) This too was for an abortive project, webperl, an application of Don Knuth's WEB system of structured documentation to Perl. However, given the code quality of these two modules, it's perhaps just as well that the projects never saw the light of day.

There are a few other modules I'd rather like to forget, too. Devel::Pointer was a sick joke that went badly wrong - it allowed people to use pointers in Perl. Some people failed to notice that referring to memory locations directly in an extremely high-level language was a dangerous and silly thing to do, and actually used the damned thing, and I started getting requests for support for it. Then at some point in 2001, when I should really have known better, I developed an interest in Microsoft's .NET and the C# language, which I still think is pretty neat; but I decided it might be a good idea to translate the Mono project's tokenizer and parser into Perl, ending up with C::Sharp. I never got around to doing the parser part, or indeed anything else with it, and so it died a lonely death in a dark corner of CPAN. GTK::HandyClist was my foray into programming graphical applications, which started and ended there. Bundle::SDK::SIMON was actually the slides from a talk on my top ten favourite CPAN modules - except that this changes so quickly over time, it doesn't really make much sense any more.

Finally, Array::FileReader was an attempt to optimize a file access process. Unfortunately, my "optimization" ended up introducing more overheads than the naive solution. It all goes to show. Since then, Mark-Jason Dominus, another huge influence in the development of my CPAN career, has written Tie::File, which not only has a better name but is actually efficient too.

The Internals Phase

1999-2000 were disastrous years for me personally but magnificent years Perl-sonally. Stuck in a boring job and a tiny flat in the middle of Tokyo, I had plenty of time to get stuck into more Perl development. I felt that getting involved with perl5-porters would be a good way of gettting to know more about Perl, and so I needed a hobby horse - an issue of Perl's development that I cared about. Since I was in Japan and working a lot with non-Latin text, Unicode support seemed a good thing to work on, and so Unicode::Decompose appeared, while I fixed up a substantial part of the post-5.6 core Unicode support.

I'd recommend this way to anyone who wants to get more involved in the Perl community, although I was very lucky in terms of who else happened to be around at the time: Gurusamy Sarathy was extremely gracious in helping me turn my fledgling C code into something fit for the Perl core, and he also helped me understand the perl5-porters etiquette (yes, there was some at the time) and what makes a good patch, while Jarkko Hietaniemi was always good for suggestions of interesting things for keen people to work on. Seriously, get involved. If I can do it, anyone can.

Anyway, this fixation with understanding the Perl 5 internals, and especially the Perl 5 compiler, (due to yet another of my Perl influences, the great Malcolm Beattie) led to quite a torrent of modules, from ByteCache, an implementation of just-in-time compilation for Perl modules, through B::Flags and B::Tree to help visualising the Perl op tree, to uninit, B::Generate, optimizer and B::Utils for modifying it.

Perl About The House

Now we abandon chronological order somewhat and take a look at the various areas in which I've used Perl. One of these areas has been the automation of everyday life: checking my bank balance with Finance::Bank::LloydsTSB (the first Perl module to interface to personal internet banking, no less) and my phone bill with a release of Tony Bowden's Data::BT::PhoneBill.

Finance::Bank::LloydsTSB was meant to go with Finance::QIF, my Quicken file parser, to produce another now-abandoned idea, a Perl finances manager. It seemed that I'm only capable of producing modules, not full standalone applications - or at least, it seemed that way until I produced Bryar, my blogging software, based on the concepts from Rael Dornfest's blosxom and beginning my adventures with Andy Wardley's Template Toolkit. Bryar also tuned me in to the Model-View-Controller framework idea, of which more later.

Another project I briefly played with was a personal robot, using the Sphinx/Festival speech handling and recognition modules from Cepstral and Kevin Lenzo. I didn't have X10, so I couldn't shout "lights" into the air in a wonderfully scifi way, but I could shout "mail" and have a summary of my inbox read to me, "news" to get the latest BBC news headlines, and "time" to hear the time. Of course, getting computers to tell the time nicely takes a little bit of work. I don't like "It's eleven oh-three pee em", since that's not what someone would say if you asked them the time. I wanted my robot to say "It's just after eleven", and that's what Time::Human does. Shame about the localisation.

Messing About With Classes

One of the things that continues to amaze me about Perl is its flexibility; the way you can change core parts of its operation, even from pure Perl. This lead to quite a few modules, many of which were mere proofs of concept.

Sub::Versive, for instance, was the first module on CPAN to handle pre- and post-hooks for a subroutine; it has since been joined by a plethora of imitators. It was written, though, in response to a peculiar scenario. I was writing a module (Safety::First) which provided additional built-in-like functions for Perl to encourage and facilitate defensive programming and intelligible error reporting. ("Couldn't open file? Why not?") These built-ins had to be available from every package, which meant playing with UNIVERSAL::AUTOLOAD. But what if another package was already using UNIVERSAL::AUTOLOAD? Hence, Sub::Versive wrapped it in a pre-hook. Of course, with the interesting bit of the problem solved, Safety::First was abandoned.

Class::Dynamic was an interesting attempt to provide support for code references in @ISA, analogous to code references in @INC. It works, but of course I could never find any practical use for it.

Class::Wrap was written as a lazy profiler. A certain application I was writing for my employer of the time, Kasei, made use of the (IMHO evil) Mail::Message module. How do we isolate all calls to that class? There are plenty of modules out there for instrumenting individual methods, including of course Sub::Versive. But the whole class? Class::Wrap takes a wonderfully brute-force but workable approach to the problem. A real profiler, however, can be constructed from Devel::DProfPP, which is sort of a profiler toolkit.

I wrote a couple of other modules with Kasei in this category, particularly while working on our Plucene port of the Lucene search engine. (I guess I could claim Plucene as one of my 100 modules, but that would be to deny Marc Kerr the recognition he deserves for the work he put in to packaging, documenting and providing tests for my insane and scrambled code.) I wrote Bit::Vector::Minimal, for instance, as I ported org.apache.lucene.util.BitVector; Tie::Array::Stored, which I'm amazed wasn't already implemented on CPAN, provided the Perl equivalent of org.apache.lucene.util.PriorityQueue. Lucene::QueryParser, of course, does what it says on the tin. (I also produced a couple of add-ons for Plucene after leaving Kasei when I was doing a bit of Plucene consultancy: Plucene::Plugin::Analyzer::PorterAnalyzer and Plucene::Plugin::WeightedQueryParser.)

Another module produced in the course of writing Plucene was Class::HasA, a handy little utility module which works well with Tony Bowden's Class::Accessor and merely dispatches certain method calls to objects contained within your object.

And speaking of Class::Accessor, Class::Accessor::Assert would have been a godsend while writing Plucene, as it's a version of accessor handling which typechecks what you're putting into the accessor slots. When you're converting a typed language into an untyped one, occasional checks that you're handling the right kind of object don't go amiss. I learnt my lesson eventually, though, and wrote the module after Plucene was done.

Another Java-influenced module was Attribute::Final, which was written for my book Advanced Perl Programming as an example of both attributes and messing about with the class module - by marking some subtourines as :final, you get an error if a derived class attempts to override it. As with many of my proof-of-concept modules, this isn't something I'd ever use myself, but I know others have used it. I'll let you into a secret - over the past few months I've settled on giving modules a version number of 0.x if I've never used them myself and 1.x if I have.

Java wasn't the only language to influence my Perl coding activities. Ruby is a wonderful little language I first encountered in Japan, but didn't really get into until around 2003. Of course, when you see another language has dome good ideas, you steal them, which is what I did with rubyisms, SUPER, and Class::SingletonMethod - all of which, by the way, are excellent examples of what you can do to the behaviour of Perl just from pure Perl. SUPER is the kind of module I've so often wanted to use in production code but never dared.

Smart Perl

My views on human-computer interface and computer usability have been unchanged since I wrote Tie::DiscoveryHash way back in the mists of time. The underlying principle behind that module was simple: the user should never tell the computer anything it already knows or can reasonably be expected to work out. Tie::DiscoveryHash was all about having the computer find out stuff for itself.

This has influenced a number of my modules, which have focussed on trying to make everything as simple as possible for the user (or more usually, for the programmer using my modules) and then a bit simpler.

So, for instance, I found the whole process of keeping values persistent between runs of Perl a bit of a nightmare - I could never remember the syntax for tying to DB_File, and I would always forget to use the extremely handy MLDBM module. I just wanted to say "keep this variable around". Attribute::Persistent does just that, cleanly and simply. It even works out a sensible place to put the database, so you don't have to.

Similarly, Config::Auto works out where your application might keep a configuration file, works out what format it's in, parses it, and hands you back a hash. No muss, no fuss. And more importantly, no need to even think about writing a config file parser again. It's done once, forever. Getopt::Auto applies the same design principles to handling command line arguments - I hate forgetting how to use Getopt::Long.

Other attempts at making things simple for the end-user weren't that successful. As part of writing my (first) mail archiving and indexing program, Mail::Miner, of which more later, I wanted a nice way for users to specify a time period in which they're looking for mails - "a week ago", "sometime last summer", "near the beginning of last month" - and so on. Date::PeriodParser would take these descriptions and turn them into a start and end time in which to search. Except, of course, that this is a very hard thing to do and requires a lot of heuristics, and while I started off quite well, as ever, I got distracted with other interesting and considerably more tractable problems.

Mail Handling

A good number of my Perl modules focussed on mail handling, so many that I was actually able to get a job basically doing mail processing in Perl. It all started with Mail::Audit. I was introduced to procmail at University, and it was useful enough, but it kept having locking problems and losing my mail, and I didn't really understand it, to be honest, so I wanted to write my mail filtering rules in Perl. Mail::Audit worked well for a couple of years before it grew into an obese monster. I actually only use a very old version of Mail::Audit on my production server.

As part of the attempt to slim it back down again, I abstracted out one of the major parts of its functionality, delivering an email to a local mailbox. Now I only use mbox files, so it was reasonably easy for me, but people wanted me to add Maildir and whatever to Mail::Audit, so I kicked it all out to Mail::LocalDelivery instead.

But I found that I still wasn't able to filter my mail adequately and find the stuff I needed from it. Attachments were a big problem, since they both made ordinary search with grep or grepmail much slower, and they weren't always easy to find anyway. So I wrote something to remove attachments from mail and stick them in a database, and while I'm at it, index mail for quick retrieval. And then it grew to identifying "interesting" features of an email and searching for them too, and then Mail::Miner was born.

Finally, I got into web display of archived email, and needed a way of displaying threads. Amazingly, nobody had coded up JWZ's mail threading algorithm in Perl yet, so I did that too: Mail::Thread.

But then I decided that Mail::* was in a very sick state. I had been working with the mail handling modules from CPAN - including my own - and grown to hate them; they were all too slow, too complicated, too buggy or all three. It was time for action, and the Perl Email Project was born.

Email::Simple was the first thing to come out of this, and is a fantastic way of just getting at the bits you need from an email. It's much simpler, and therefore much faster, than its more fully-featured cousins on CPAN. Email::MIME was its natural successor, which added rudimentary MIME handling, and spawned two subsidiary modules, Email::MIME::ContentType and Email::MIME::Encodings in order to keep Email::MIME itself focussed on the "do one thing and do it well" principle.

Of course we then had to replace Mail::Audit, so Email::LocalDelivery and Email::Filter appeared. This is another module I don't use, because my Mail::Audit setup works and I'm terrified of breaking it and losing all my mail. But I'm told that Email::Filter works just fine too.

By this stage, Mail::Miner was getting crufty. It was replaced by a much more modular and beautiful Email::Store; this is extended with plug-in modules like Email::Store::Summary, Email::Store::Plucene and Email::Store::Thread. I had to write the plug-in framework myself, since neither Module::Pluggable or Class::Trigger did quite what I wanted, and so the Email::Store project also produced Module::Pluggable::Ordered.

Now Email::Store naturally uses Email::Simple objects, since it's the most efficient mail representation class on CPAN. Unfortunately, Email::Store also wants to make use of some modules on CPAN like Mail::ListDetector which don't want to know about Email::Simple objects and want to talk Mail::Internet or whatever. To get around this, I wrote Email::Abstract which provides module writers with an interface to any kind of mail object, so they don't have to force a particular representation on their users.


I'm actually a linguist by training, not a computer programmer, graduating from the school of Oriental Studies with second and third year options in Japanese linguistics. I'd like to think that my work at Kasei was as much about linguistic and textual analysis as it was about mail munging. With that in mind, I wrote a few language-related modules during my time with them.

The first important module, which I started work on while I was playing with Mail::Miner, was Lingua::EN::Keywords. This started life as a relatively naive algorithm for picking common words out of a text in an attempt to provide some keywords to describe what the text is "about", and has matured into quite a handy little automatic topic recognition module. Its natural counterpart is Lingua::EN::NamedEntity, which is still a naive algorithm but sometimes those are the best ones.

This module has a bit of story behind it. While analysing mails we were trying to find people, places, times, and other things we could link together into a knowledge base. The technical term for this is named entity extraction. I find a useful library to do this, called GATE. It's written in Java, which meant using Inline::Java, and is extremely slow and complex. At the same time, I was writing a chapter on computational linguistics with Perl in Advanced Perl Programming, and wanted to talk about named entity extraction. Unfortunately, I only had one module which did this, GATE::ANNIE::Simple, and it was a hack. If you're going to talk about a subject, it makes sense to compare and contrast different solutions, and Tony had already been saying "why don't you just write something to pull out capitalized phrases, for starters?" I did this, intending to use it as a baseline, but of course it's much faster than GATE and not noticably less accurate. Ho hum.

Another thing those wacky computational linguists do a lot of is working with n-gram streams. In every discipline, there's a particular hammer you can use to solve any given problem. In data mining, it's called market basket analysis. In computational linguistics, it's maximal entropy. You look at the past stream of n characters (that's an n-gram) and work out how hard it is to see what's coming next.

For instance, if I feed you the 4-gram xylo the chances of a p next are very high. The chances of a e, or indeed anything else, are pretty low. Low entropy area. But if I feed you then, it's really not easy to guess the next letter, since we're likely to be at the end of a word and the next word might be anything; high entropy. That's how you use maximal entropy to find word breaks in unsegmented text, and there's a huge amount of other cool stuff you can do with it.

I swear the day I wrote Text::Ngram, there were no other modules on CPAN which extracted n-grams, but as soon as I released it it looked like there were three or four there all along. (Including one from Jarkko, no less.) Anyway, I wanted to see if I could still remember how to write XS modules, especially since I'd just written a book about it.

Lingua::EN::Inflect::Number is a terrible hack, but it works. I needed it to make Class::DBI::Relationship (of which more later) more human-friendly. Lingua::EN::FindNumber is another hack written for APP; I was a little surprised that Lingua::EN::Words2Nums, which is a fantastic module in its own right, can turn English descriptions of numbers into digits, but it can't actually pull the numbers out of a text in the first place. So I fixed that.

Text Munging, and Some More Mail Stuff

Applying my linguistic experience to the problems of intelligent mail indexing, searching and displaying led to churning out another set of modules.

The first problem was what to do with search results. You know those little snippets that Google and other search engines display when you search for some terms? They contextualise the terms in the body of the document and highlight them in a snippet that best represents how they're used in the document. This is actually a really hard problem, and it took me several goes to get Text::Context right. It uses Text::Context::EitherSide as an "emergency" contextualizer if it can't get anything right at all, but the algorithm itself is a bit of a swine. I actually had to prototype this module in Ruby to get my thinking clear enough to code it up in Perl...

Text::Quoted was another mail display problem - it's nice to display different layers of quoted text in an email in different colours. Identifying the quoted text isn't that hard, but working out a particular bit nests is also surprisingly tricky. So I sorted it out.

The next problem I had to solve lead on from this. Suppose you've got some mail, which is plain text, and you're going to display it as HTML. Along the way, you want to turn any URIs into links, (maybe using something like URI::Find::Schemeless::Stricter to find things which look like URLs, but which doesn't think that numbered lists are IP addresses) escape any non-HTML-safe characters, highlight search terms, put different quoted regions in different colours, and maybe do other things too. The thing is, you have to be very careful about the order in which you do this. Once you've escaped the HTML, you might mess up your colouring of quoted text, but if you've turned the URIs into links first, you'll mess them up when you escape all the HTML entities. Text::Decorator allows you to do all these transformations in a nice, safe way, "layering" things like URI escaping, highlighting, and so on, and then rendering to text or HTML or whatever when all the layers have been applied.

Text::Decorator was written in a meta-programming system I wrote called pool, which I should probably use more. It writes the boring bit of OO classes for you given a simple description of the methods and attributes.

Oh, and if you're not contextualising search terms in a mail snippet, you probably just want to display the original content rather than the first few lines, which invariablely contain lots of quoting of another message. Text::Original, extracted from the code of the Mariachi project and so actually only packaged by me and written by Richard Clamp and Simon Wistor, does just this.

WWW::Hotmail was an attempt to solve the problem of how to import all the mail a user already has into our archiving program, a problem Gmail is now dealing with. Actually, Gmail's currently dealing with pretty much all the problems we looked at last year. It's quite funny, really.

SIMON Hits The Web

I hate web programming. HTML is boring, CGI is boring, and I tried avoiding it for as long as I could. This stopped when I worked for Oxford University, handling their webmail service, which lead to Bundle::WING. Also at Oxford, I had to work with AxKit, which caused me innumerable headaches but I finally got some working XSP applications written, not without writing the Apache::AxKit::Language::XSP::ObjectTaglib and AxKit::XSP::Minisession helper modules. I also did some playing around with mod_perl, thanks to the rather wonderful mod_perl Cookbook, and came up with Apache::OneTimeURL when, during a particularly paranoid phase, I wanted to give out my physical address in URLs that would self-destruct after a single reading.

After leaving, though, I discovered the Class::DBI/Template Toolkit pair which has dominated my web programming since then. If you haven't played with these two modules yet, you really need to, since they work so well together, and with other modules like CGI::Untaint, that they simplify so much of web and database work. I extended CGI::Untaint with a bunch of extra patterns while at Kasei and afterwards, including CGI::Untaint::ipaddress, CGI::Untaint::upload and CGI::Untaint::html, I also wrote a whole plethora of CDBI extensions: Class::DBI::AsForm, Class::DBI::Plugin::Type, Class::DBI::Loader::GraphViz (reflecting my penchant for data visualization), and Class::DBI::Loader::Relationship, which applies the "as simple as possible and a bit simpler" approach to defining data relationships.

The whole culmination of CDBI, TT, and all these other technologies came when I sat down and wrote Maypole, a Model-View-Controller framework with, again, emphasis on making things very simple to get working. The Perl Foundation's sponsorship of Maypole development has been one of the proudest achievements in my CPAN career, and lead not only to a stonking big manual, loads of examples, but also Maypole::Authentication::UserSessionCookie and Maypole::Component.

Template Toolkit and XML came back together again in a recent project where I've had render some XML as part of a Maypole application. Amazingly, there wasn't an XSLT filter for the Template Toolkit, so Template::Plugin::XSLT was born.

Games, Diversions and Toys

It was only when I got back from Japan that I learnt to play Go. How stupid was that. For a year I had access to some of the best Go clubs and professional teacher and players in the world, and then I only pick the bloody game up when I get back to England. Anyway, any computer programmer who learns to play go, and they all do soon or later, eventually decides to do something about the pitiful state of computer Go. It's quite ridiculous that the game's been around for thousands of years and the best computer programs we've devised regularly get beaten resoundingly by small children. Anyway, I did my bit, producing Games::Go::GMP and Games::Go::SGF as utility libraries, before working on Games::Goban to represent the state of the game.

But then while working for Kasei we discovered another addictive diversion: poker. Computer poker isn't that great either, and I wanted to write some robots to play on the internet poker servers; Games::Poker::HandEvaluator was the first product there, with the hard work done by a GNU library, and Games::Poker::OPP being the interface to the network protocol. The comments to that module contain a large number of Prisoner references, for no apparent reason. OPP needed a way of representing the state of a poker game, so I wrote Games::Poker::TexasHold'em to do that. And also because it was a fantastic abuse of the ' package separator.

Oh, and another of my early modules that refused to die was Oxford::Calendar, which converts between the academic calendar and the rest of the world's. It all counts, you know.

The Future

I've had mixed feelings on Perl 6, starting with my very public nightmare at its announcement in 1999, (Hey, I'd just written a book on Perl 5 internals, and now they're telling me it's obsolete.) and then my very public repentance in 2000, at which point I was very excited about the whole thing. So much so, that I produced vast numbers of design documents for the language, most of which now ignored, but that's OK, and set to work helping Dan design the core of the interpreter too. In fact, I somehow managed to do so much work on it that, after a hacking session together at O'Reilly in Boston in 2001, Dan let me be the release pumpking of parrot, a job I did until life got busy in 2002. I'm extremely happy to have been involved in that, and hope I didn't start the project off on too much of a bad footing. It looks to be doing fine now, at least.

I was still interested in how they're going to make the Perl 6 parser work, (I still am, but don't have enough time to throw at the problem) and with my linguistic background I've always been interested in writing parsers in general. So early on I started trying to write a Perl6::Tokener, which is now unfortunately quite obsolete, with the intention of writing a parser later on. For most of 2002, my whiteboard at home was covered with sketches of the Perl 6 grammar.

Then I found out that the parser is actually going to be dynamic - you can reconfigure the grammar at runtime. Hey, I thought, that's going to be fun. At this point, you can't use an ordinary state-table parser like yacc, as Perl has done so far, because that pre-computes the transitions up front. Instead, you have to use a proper state machine without pre-computed tables. But I couldn't find any parsers which worked on that basis, so I wrote one, shishi, prototyping it in Perl with Shishi::Prototype first.

This work has been largely ignored, unfortunately, but that's because mainly I haven't had the time to do interesting user-facing stuff on top of it so that it can be shown off. I tried porting Parse::RecDescent to it (using Parse::RecDescent::Deparse to figure out what P::RD was doing) to produce a much faster recursive descent parser, but when I heard that Damian Conway was funded to work on Parse::FastDescent and Parse::Perl, (yes, I have a prototype of that too) I decided to leave him to it. After all, why should I do the work and have other people get paid for it? These modules did not materialise, but then, a failure on his part does not constitute necessity on mine.

While I was messing with Parrot, I wanted to get other languages running on the VM too, including Python, so I wrote Python::Bytecode to take apart the Python bytecode format so that it can be reassembled as Parrot IMCC. Thankfully, Dan's taken this over, updated it for the latest version of Python, and seems to be making good use of it converting Python libraries to Parrot.

And the final joke...

I'm fond of a good joke, the Parrot April Fool's Joke being my pinnacle, but I have mixed feelings about the Acme:: namespace on CPAN. I don't know why. The thing is that I'd prefer modules which are funny because they're clever, rather than modules which claim to be funny because they're copies of other modules that claim to be funny. So my contributions to Acme::* have been deadly serious.

Acme::Dot, for instance, is another example of how much you can warp Perl's syntax without resorting to source filters. You can call methods Ruby-style with the dot operator. But it's still the dot operator. You work that one out.

And my other contribution to Acme::* - and my hundredth module? Well, you've just finished reading it.


Simon Cozens,