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The Joy of Perl

Document Information

By: Shlomi Fish

Date: 11-December-2003 (converted to HTML, fixed and updated at 09-October-2005)

Last Updated: 18-February-2009 (converted to Website Meta Language, integrated into the main flow of the site, and added a rudimentary table of contents)

Licence

Creative Commons License

This document is Copyright by Shlomi Fish, 2003, and is available under the terms of the Creative Commons Attribution License 3.0 Unported (or at your option any later version of that licence).

For securing additional rights, please contact Shlomi Fish and see the explicit requirements that are being spelt from abiding by that licence.

My Perl History

When I first learned the Perl programming language, I was working right after high-school as a C/C++ Windows systems programmer in a small startup. The job was very interesting, but the pay was very low and so I was looking for a better job. My friend introduced me to a Ran Eilam who was about to finish his university degree and was planning on starting up his own web-publishing firm. The year was 1996, and it was the beginning of the Internet craze.

I went to Tel Aviv university, where I met Ran. He accepted me to the job and said I should learn Perl. Having told him I knew about Berkeley Sockets, (from my previous workplace) he said that one can write a sockets client in Perl in 10 lines and a server in 20 lines. He showed a piece of Perl code he wrote to handle a client’s request, which seemed awfully short. I did not understand what was going on there.

Between Jobs I was given time to adapt to the new workplace. Ran said: “Shlomi, it takes 10 years to learn UNIX. I want you to learn it in a month”. I set out to install Linux and experiment with UNIX and Perl. When I got the job, I read the Perl man pages (which I downloaded in PDF format), and also was able to experiment a bit with Linux.

Needless to say, I was not able to learn UNIX as thoroughly as Ran would have wished to believe I could. (I can testify that my knowledge back then was very superficial in comparison to my current one). But I knew it well enough, and learned more as time went by, to make myself useful there.

I can say that the experience was nothing less than revolving. UNIX was an epiphany for me. For the first time in my life, I found a system that worked and behaved like it should. Until then, during the time I experienced with DOS and Windows 3.x, I knew these systems were bad, but I could not tell exactly why, because I did not have any point of reference. UNIX, on the other hand, was a completely logical (albeit sometimes not entirely consistent) system, that was a joy to work with, even with my superficial mastery of it.

Perl, in a way, was a revelation as well. I finally found a language that was not only fun to program with (as was the case with BASIC), but also very practical and usable. It had everything C and BASIC had and more. It immediately became my favourite language (and still is).

Back then, I even wrote my “shell scripts” in Perl since I hadn’t taken the time to learn shell well. (Since then, I’ve known of other people who have followed this trend, and learned shell programming only after learning Perl, and I expect this trend to grow.)

My knowledge of Perl was almost as superficial as my knowledge of UNIX. I knew a large part of syntax, the constructs, the basic data structures, the regular expressions, and even took the time to learn to use references and nested data structures. However, I did not know how to write modules, much less objects, and there were many details in the man pages that I did not pay much attention too. Furthermore, my knowledge of what was present in CPAN was inadequate and I often re-invented many wheels time and again.

As I went to a different Windows-oriented workplace, I installed Perl and a UNIX-like environment there. In due time, I learned from experiencing more about UNIX and more about Perl. A few years down the road, I learned how to write my own modules and even later on how to write objects (both were surprisingly easy). I also became familiar with other details and paradigms of the language, and also now know better how to search for something in CPAN (and even, gasp, how to use the CPAN.pm module to automatically install things) so I don’t re-invent too many wheels as before.

Why I like Perl so much

I like the fact that Perl is orthogonal and does not force the poor programmer who wishes to learn it to learn too many paradigms. In Java, for example, the “Hello World” involves initializing a class and several methods, only to call the uncivil “System.out.println("Hello World");”. In Perl, it is simply

print "Hello World!\n"

And you can leave Object Oriented Programming out of it. Furthermore, while you can use closures; map, grep, sort and friends; objects and inheritance; modules, etc. you are not forced to use them if you don’t want to or don’t know how. Perl is a language that grows with you, and does not force you to learn all of it in a day.

Some languages (C and Scheme come to mind) are minimalistic. You can learn them almost entirely after a while and afterwards, nothing will surprise you. Even if you do encounter a new keyword or a new built-in function, you are not surprised. Most of the time it was found because you needed to do something like that, and figured out it must exist.

This is not the case for Perl. In Perl, I constantly felt (and other people shared my sentiments) that I am learning new things all the time. Not only that, but they are very enlightening and immediately prove useful in future programs.

Many times I found paradigms in other languages or books and discovered they were readily applicable in Perl. For instance, after reading the excellent book “Structure and Interpretation of Computer Programs” and seeing how closures could prove to be useful, I tried it in Perl and it immediately worked. From then on, I sometimes found myself using closures in Perl.

Another thing that is great about Perl is that it is useful for performing practical tasks. In some languages I encountered, like Scheme or Haskell, one always get the feeling that while being nice to play with, they cannot be effectively used for anything practical. This is not the case for Perl, that provides both usable and intuitive syntactical primitives as well as many primitives and open source API’s for calling the services of the system. This is one property that is shared (to a lesser or greater extent) by similar languages such as Python, Ruby or PHP.

What makes Perl quite unique among most languages, is its “There’s more than one way to do it” philosophy. I, actually, am very fond of this. Any time I write a script or a module, (even a very trivial one) I am glad I have several ways I can think of to write it. Contrast this with Python’s “There’s one good way to do it”, in which the language designers tried to create a unified way for programmers to use it. If you ask me, a programming language in which “there’s only one way to do it” is almost as bad as a spoken language in which “there’s only one way to say it”. Such a language may be easy to learn, but it certainly won’t be fun to use. Neither are such programming languages.

Larry Wall once noted that Perl in essence tries to be the Tower of Babel of the programming languages. That you can write Python in Perl, and LISP in Perl, and BASIC in Perl, and C in Perl. All of this diversity comes with a cost, as many newcomers will find reading the Perl code of expert programmers (or of their peers with a different education) very difficult. It’s probably similar trying to understand a text of English by a very knowledgeable writer when you’ve only studied it for 6 months.

However, I believe that despite common belief, Perl code is not hard to understand more than other languages. (unless it’s purposely obfuscated). You just have to be familiar with more idioms, and conventions. It takes some time, but it’s well worth it. Of course, it is possible that you won’t understand what the algorithm of the program is doing. But you can encounter the latter problem in any language regardless of how rich or poor it is in programming paradigms.

Perl is also a no-nonsense language. I’m reminded of a time when a person I know from my university was assigned to write a web-based system for managing the lab he was working in. He decided that Perl, PHP and Python all sucked and would rather use his favourite language: C++. It took him over a year and he did not finish, in what I would estimate as a one month project using either Perl, PHP or Python. In the midst of this, he kept telling me about the “beautiful abstractions” he built in C++. Every time, I kept telling him that in Perl it was equally or more trivial to do.

In C++, one can be tempted to write templates upon templates and classes upon classes, trying to accomplish what a Perl programmer takes for granted, or can easily leave alone as a necessary pattern in the code. So, in a sense it is not a no-nonsense language. Java and ANSI C are much better, in that sense. Thus, one does not need to wonder why most compiled open source software is written in C, including the interpreters and back-ends for some highly object oriented languages.

You can hear many complaints about the Perl syntax. (I even heard that Perl is “a syntactical disaster”). However, I actually like it. The reason is that I can immediately tell what’s going on by looking at the code. If I see a dollar sign it usually indicates that there’s a scalar involved. If I see square brackets, I know it’s an array subscript, etc. Larry Wall said in one of his speeches, that in LISP all the code comes in parenthesis, so all the code looks the same. Perl is the exact opposite of LISP, in this regard, and a Perl code brings out the data structures and operations that are performed.

Perl has spawned an interesting culture around it. From countless local Perl mongers groups, to mailing lists dedicated to any Perl topic, to the many modules of CPAN (some of which are downright useless, but still fun), to many web-sites with lots of good resources there. In fact, it is very fun being a part of the Perl community, which cares about so much more than writing Perl code for a living. (even though many people do that and there’s nothing wrong with it). For the Perl community, Perl is fun, and it keeps trying to find more fun things to do with it.

Larry Wall as a Linguist, tried to make Perl feel like a natural language. And it indeed does, more than any other language I have encountered. I, recall an incident that happened to me in high school. In English class, we were taught about forming speeches (the standard “First of all,”, “Moreover/Furthermore”, “To sum up” stuff). Then we played the balloon game: we were split into teams and given an assignment to write a speech together, in which we had to explain why we of all the other people in the balloon had to be saved.

Now, most of the speeches given in class were quite mechanical: “First of all… moreover… furthermore… to sum up,”. I, however, assumed the role of President Roosevelt after the Pearl Harbor attack, and wrote a nice speech in which I don’t think I’ve used any of these key-words once. (I also volunteered to give the speech first and so was able to read it from the paper). It ended up being the Teacher’s favourite, and won third place. (because two of the other speeches were funny, but in my humble and prejudiced opinion, quite lame as well)

The moral of the story is, that you can’t survive with knowing the technique alone when writing prose. You need to know how to make it flow together. In a sense Perl is not about technique alone. Knowing the syntax, the keywords and the functions can only get you so far. But you still need to know how to write beautiful programs that will make the one who reads them say “Wow!”. To quote Abelman and Sussman from Structure and Interpretation of Computer Programs: “Programs should be written for people to read, and only incidentally for machines to execute.”

Recent History

A couple of years ago, life was brought into the dormant Israeli Perl community. A web-site was being maintained, monthly meetings are now the norm, and there’s also an active mailing list. We even had a perl conference (YAPC::Israel::2003) and planning to have another one. I am grateful for the people who made this happen.

I don’t know how much we were able to introduce more people to using Perl in Israel, but we certainly have a lot of fun learning new things from each other.

I now meet Ran Eilam (who as you may remember introduced me to Perl in the first place), in our monthly meetings. Having spent the time we were apart in the industry working for his living, he is now full of various industry trends (and hypes), advocates Extreme Programming and calls user-interface geometry managers, “the geometry manager pattern”. (I guess that what happens during all the time you spend studying in university, and hacking on open-source software) He still seems to be very productive, and gave some very good presentations to the local Perl Mongers.

I still did not spend the time I learned in the Technion doing nothing. I did my best to learn as much as possible about UNIX and Perl (which I think is the language that encompasses its spirit in the best way). I recently read the third edition of the Camel Book which I borrowed from the Perl Mongers Library. I learned so many new things as I have read it (even though beforehand, I was by no means a Perl newcomer), that I had to buy it. (which I did)

I don’t regret specializing in UNIX and Perl. One constantly hear about all those over-hyped technologies: the Java world on one end and the Windows and .NET on the other. Don’t get me started for my opinion of Windows - I don’t work on it, except if I don’t have a choice. Java is a nice language, but shivers in comparison to Perl. .NET seems like something a bit better than Java, but still closer to it than Perl. I’ll take the time to learn it, if and when I need to. (its promises of cross-language programming are pretty void, because it’s mostly the same language with a few syntactical differences).

UNIX and Perl both seem to have a bright future ahead of them. They may not have the hype machine that other technologies have, and nor do they desire them. But they are both very rich, usable and functional technologies, and their quality speak for itself.

Eric Raymond claims in The Art of UNIX Programming this:

Python has risen in popularity as rapidly as Tcl has fallen. Though the Perl community is still twice the size of Python’s, a visible tendency of the brightest Perl hackers to migrate to Python has been rather ominous for the former language, especially as there is no migration at all in the opposite direction.

I’m not sure if I qualify as one of the brightest Perl programmers (after all, the baker cannot testify for his dough). But I know a few very bright Perl programmers who avoid Python like the plague. And I don’t see prominent Perl figures like Larry Wall, Tom Christiansen, Randal L. Schwartz, Damian Conway, Mark Jason Dominus, etc. converting to Python. (even though I’m pretty sure they know it well). I think this trend is an indication of a fact: Perl is not for everybody. All the qualities I described can sometimes lure people away from it into the beauty of the much different Python. And that’s good, because, I don’t think one language can actually be suitable for everybody, and I’d rather have co-programmers who _love_ the languages they program in. (and for the record, I read something by someone who claimed Java was much better than either Perl, Python or Tcl, so you can’t tell)

But Python is not for me. Once, a distinguished Haifa Linux Club member gave a lecture about Python, and after looking at his slides, I wrote to him to tell him that they convinced me that Python was not my cup of tea. Moreover, during the presentation itself, I asked him if some of my favourite features in Perl were present there, and almost always consistently discovered that they were not. Needless to say, it did not make me more convinced.

So, I don’t think we should feel intimidated by Python any time now. Not any more than cats should be intimidated by dogs for people’s affection. (I’m not trying to make a generalization between the two divisions - there isn’t any).

So, keep the Shift key and the “4” key on your keyboards in working order, because you’ll need to use them a lot in your future.