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Closed 10 years ago.
I got into Perl years ago and always found it a fun and expressive language to work with.
I found that programming in Perl makes me quite productive thanks to its low overhead and the outstanding amount of ready-made solutions to common problems on CPAN.
If you're new to Perl, what got you into it?
I was coding PHP for a living, and then heard of their change from :: to \ as a name-space separator. I'm really not joking or being spiteful, but that is really what got the ball rolling.
Not to be elitist, but I suddenly realised that the people I had to collaborate with whom knew PHP understood very little in programming concepts in ways that frustrated me how they could be so blind, the people in the IRC rooms for it were no longer a source of help for my questions, and I usually spent more time answering questions and waiting for somebody to turn up whom could answer mine. Usually I ended up solving it myself.
Most the time I realised was people re-solving the same problems over and over again in increasingly bad ways.
I discovered problematic behaviours in PHP which defied logic and reasoning (like the array_merge_recursive family), and discovered functions that were undocumented in how to use them, and when I reported a bug in the functions, my bug was marked as "Bogus" and I was expected to be psychic.
I had a friend whom was constantly proclaiming the goodness of Perl, so I basically gave it a shot and now am hooked like an addict.
Additionally, my experience in other higher-order dynamically typed languages (JavaScript and Ruby, yes, JavaScript is a more powerful language than PHP in terms of language features) left me a knowledge with many ways to solve types of problems easily, but being restricted in such a way I had no way to use these powerful features. Perl satisfied this need.
Why Perl and not Ruby? I've played with Ruby a bit, but my experience taught me the support and documentation is sparse, the language is slow and immature. Nice it may be, but its still in diminished in capacity against Perl from what I've seen. And it shared PHPs major flaw that it has a huge user base comprised of total novices all doing things the wrong way, and I really wanted to not have to deal with that so much.
It's not nice to be elitist, but once you have tried to explain the same thing to 30 people (and taken an hour to get a simple concept into their heads every time) it reaches a point of frustration. (I can't cope with the 'There is somebody on the internet who is wrong' situation, If I can't SEE it, it doesn't happen)
I started doing Perl during my third year in computer science as a part of 'Scripting languages' course. I have a friend studying biotechnology and I helped her with some data mining scripts for dealing with protein databases (parsing text files, regexps, simple integrity checks). It was all very natural to do in Perl.
Then I got my first part-time job and had to use it professionally. I was responsible for developing set of batch scripts that handled some part of business logic in the company. And it was the task where Perl revealed all its potential. Need to get data from DB? - no problem, just go to CPAN. Need to automate wiki - no problem, go to CPAN. The amount of already created modules is overwhelming and you can be sure you will always find what you need in CPAN.
To sum up. For me, Perl is a swiss army knife of scripting languages. Everything can be done in it and it has huge number of additional modules even for very exotic tasks. And by the way, did I mention REGEXPS?
With Perl (and the expressive power behind TMTOWTDI), programming becomes a creative task. I can write if($expr) { $statement; } if I plan on having many else statements, or I can write $statement if $expr; if that makes more sense (for example, I'm fond of writing:
sub doSomething {
my($toObject, $argument) = #_;
die "No object specified" unless defined($toObject);
die "Object invalid: $toObject" unless $toObject->ISA('Example');
# Do stuff
}
but of course that's not always the easiest, and most expressive way of doing it; so I come up with a better way for the task at hand!). People complain because Perl lets you write horrible looking code; I love Perl because it lets me write code which looks pretty to me (and yes, I can see the downside of having a dozen different programmers writing in their own styles; I'll hold to the idea that good writers can be pretty expressive and understandable no matter how different the subject matter).
With other programming languages, I end up having to think my way through abstraction layers (how will this Map give me Collections whose Iterators I can use to ... and so on). With Perl, I'm usually only one abstraction level above basic Perl. For instance, DBI will give me database results as ordinary, everyday Perl scalars, lists and hashes, so everything I know about these simple, core data structures carries over to every task I put DBI to (Complicated data structures? That's what PostgreSQL is for!).
I've only been using Perl full-time for about a year, but these are the big wins for me, and the reason I first went full-time onto Perl after a year suffering at the hands of Java 1.4's Collections model (don't ask). Other programming languages make me feel like I'm putting together a jigsaw puzzle, as you line up all the modules and packages just right; Perl feels like a box full of Legos, with some "special" bricks (like DBI, CGI.pm and Test::*) thrown in for good measure. There are tons of different ways to solve any problem, and Perl lets you try any of them you like, in any way you like.
I'm still not that long time in the Perl community and what me first brought in was Larry Wall's humor and wisdom. True, Perl has it quirks but the language comes from an understanding of things that is very close to mine so I'm much less comfortable with Python and to a lesser degree Ruby.
I don't do web app's more GUI with WxPerl and it works just fine. I'm very interested in languages also in lesser known like factor, boo, rebol and so on but all in all is Perl my choice. and it's because a mixture of powerful syntax (can be very functional if you like it), the community, CPAN of course, and, like I said before, due to the cosy feeling being in the right place.
Perl is its community, which is the reason to use it both on a social and practical level. (See CPAN and Perlmonks, which likely inspired SO.)
There's a lot of freedom when coding in Perl; you can write some wicked-crazy unreadable hacks, but it doesn't take long once you've gotten a feel for the language (and learned how to use perltidy :-) ) before you realize that well-written perl code can look downright pretty.
It's interesting; I ended up as a full-time Perl programmer after learning it for my sysadmin-type job in college; and now it's my strongest skill. I'm going to stick with Perl for a while because so far the language has been versatile to grow with me. I write a lot of systems software in Perl, and decided to pick up web programming for fun, and Catalyst was there waiting for me. Do I want to try out a new language paradigm? Perl will probably support it. In contrast, when I was coding in PHP for a time, I immediately felt like I was pressing against a glass ceiling.
I work as a technological troubleshooter for a big organization in southern OH. I had to learn Perl to keep some automated network text manipulation systems up and running and eventually got a little excited about it. I eventually thought of myself as a developer and wrote some programs that parsed some database data and made some people’s lives a little easier. But after reading some of the posts on this website and listening to the stackoverflow podcast and even starting to read the book Code Complete from someone’s suggested reading list I no longer have any delusions that I was a developer of Perl or any other language for that matter. However, maybe someday I could be.
I had used awk a few time for shell scripts way, way back in the days. In one ancient project we needed to implement the a TELNET protocol connection, so I wrote a quick version in Perl 4. It worked really well, and I started to really like the language.
Later, I wrote a big full commercial web application in Perl 5, complete with it's own framework and database. I was careful not to use to many of Perl's more esoteric features, so the code looked more like C than Perl. It worked really well, performance was good and the code was easily extended.
Recently I've been working in Java, but I often find myself missing the Perl's loose typing, and its ability to encapsulate things way better than Java. My favorite features were being able to put Perl datastructures (arrays and hashes) and code directly in config files and execute them, and the ability to tie code to syntax like arrays. Both lead to some really slick code.
Paul.
simple syntax, powerful scripting capabilities for win32 and unix systems, and totally powerful regex!
I pickup Perl on my first job where I had to write plenty of automation script for electrical engineers to mine datalogs and format them to Excel and sometimes deal with sql server too. With Perl I could usually get something working rather quickly, so all is good in the manufacturing land. :P
I started using Perl as an enhancement to our build process for embedded development. We needed to develop diverse outputs based on our cross compiled payload and Perl was a great fit.
Our enhancements included floating-point to hexadecimal conversion, S-record post-processing, and checksum modifications.
Not that this kind of work can't be done with many other tools, but I would definitely recommend Perl for build-related work.
What brought me to Perl was when I saw the DBI and realized that I could write the ESQL/C programs I was writing at the time in one fifth the time.
What has kept me using Perl is that the two other languages likely to unseat it are both strongly typed. That is
print "10" + 5;
is a type error rather than 15.
I'm not taking it up. I had to work on a project in Perl a few years ago, and I came to really dislike the language. It has a sometimes-awkward syntax and a lot of crazy gotchas that I found hard to work with. Honestly, I think Ruby has superseded Perl in many respects: it's good at roughly the same things, but has much nicer features and is easier to use.
Perl still has CPAN, though, which even Ruby can't match (although Ruby has a lot of useful libraries, too).
I considered learning Perl last year.
It was the only technologies that I actively decided not to learn. This is nothing directly against the language itself, it just seemed that I would be coming to the party 10 years too late. It is very useful for the shell scripting tasks that it was designed for but for me personally I prefer languages with a stronger coherence.
Perl 6 seems like it's on indefinite hiatus and even when it arrives I don't believe that it will make the language profoundly more compelling.
Also, Larry Wall scares me.
For my situation Perl wasn't the right choice and thats why.
Perl is not as bad as I thought. I used to use it in a couple customer scripts about one year ago, and even grew to like it a bit. Then again, I've never ever missed it since.
The reason? It's mostly a write-only language. Going above a 100 line solution made me be wary of my own code, which is definately not a good outcome. With other languages that bar is considerably higher (maybe 1000 or 10000 lines).
I see no reason to go for Perl in new projects, for new users, in -soon- 2009.
Related
Many standard modules are all using straight up perl -- problem is these guys arent using Moosey stuff, so I catch myself wrapping them with Moose or reinventing some simple functions in bigger libraries for convenience.
I wondered if there was any general approach to how developers using Moose incorporate other libraries that are non-Moose.
Being new to Perl and Moose I'd like to have a better understanding of how Moose is used in situations like this, or when it is generally preferred to use Moose vs Perl or even MooseX, or some other package, or whether its arbitrary.
Seems like there are different schools of thought, but Perl being as old as it is -- there are too many conflicting sources, so it's hard to navigate to a consistent truth. I'm not sure what to believe!
Anyone have a definitive source they turn to for "modern" usage of perl? Understand I've only been using perl for a month so I'm green to this community.
Updated
I don't want to hurt anybody's feelings by talking about libraries they love in a way they may not appreciate, so I've removed my side commentary about certain libraries Ive used to refocus on the question at hand.
Thanks for your guidance!
While I do not know what others do, I would be very reluctant to create myself extra work. I do not see any general need to Moosify a bunch of modules that already work.
If you want to inherit from non-Moose modules, take a look at MooseX::NonMoose.
If the HTML generation cruft in CGI.pm bothers you, you can use CGI::Simple.
About Reinventing CGI
CGI is a library which has been thoroughly tried and tested and if it needs improvement, you could build an extension, or contribute/contact the maintainers. You have to remember that modules are only as good as their track record (reliability) and their upkeep. Many people created decent modules, but didn't continue maintaining it, so they sort of fell to obscurity.
CGI is a boat all of its own, which if you think there's a lot of overhead, you could use CGI::Simple or CGI::Minimal. CGI.pm does more than parse querystrings, it also has cookie management (sessions), HTML generation, and other useful functions.
Others have had some criticisms of the overhead with CGI.pm, but that's why they developed FastCGI, which is modifying the server to use a persistent state of the script, thus loading the overhead once, rather than on every page load.
It is possible for you to create another (even better) version, but why bother? Many people may probably tell you, you shouldn't reinvent the wheel, with good reason. CGI has been around for almost 2 decades, with so many users testing it, finding holes, and having patched the holes; however, I'm never a big fan of saying "you shouldn't do something." If you think something could be better, make it better. There are many OSes that exist today just because of that reason, why settle for something that does 95% of what you need, if you need that other 5% too? But I also say, weigh your costs vs. benefits and determine if you want to devote your time to this, or if maybe there's another problem out there that has yet to be solved, that could use a little more manpower. To have something successful, you're going to need to test it thoroughly, and will most likely need to create something that other people would want and (at this point) there isn't much of a reason for CGI-users to be motivated to switch.
About Modern Perl
I think "modern Perl" is an oxymoron. I would jokingly call modern Perl; Ruby or Python.
That isn't to say that Perl isn't useful, because it is, but it's been around a long time. While it has had its significant share of changes from version to version, the most popular, Perl5, hasn't changed all that much; mind you, my definition of change is not adding to the language (new operators and functionality), but deprecating/replacing old features or changing the behavior of existing ones (like for/foreach loops).
Note: Perl6 could be considered modern perl (and does have many significant changes), but it's not widely adopted and was supposed to be released many many years ago (it's the Duke Nukem 4 Ever of programming languages).
About XS
I haven't done much module programming, but if memory serves correct, XS is the interface between Perl and C, which I think allows you to compile your perl modules for faster execution. Consider the PostgreSQL DBI module. There's a DBD::PgPP, which is a pure perl module to interface with Postgres, but there's also DBD::Pg, which I think compiles some of the code using C and takes advantage of some other OS utilities. Compiled modules have the benefit of faster load and execution (there may be some better resource management in there too).
I've looked into the source code of DBIx::Class recently and found that I don't understand a thing (though I mastered a couple tricks while trying to).
So my question is: which CPAN modules are a must read for someone who wants to learn, and in what order?
If I were doing the same I’d probably start with the ::Tiny space. I’d expect it to be less distracting—fewer edge cases cluttering things—and more idiomatic—terseness lends itself to Perl idiom—in general.
Then I’d attack the medium–large nodes from this excellent document—Map of the CPAN’s authors (large PDF). Update: Web version. Zoom into the bigger nodes then search on search.cpan.org for them. The largest nodes sometimes represent old-school and while exceptional code exists in the old school, not a lot of good teaching examples do (so I say). Authors like Miyagawa, Kennedy, and Kogman come to mind immediately as worth reviewing. There are plenty of others. Basically any module you see recommended here often, look up the author and poke around his or her other packages, as it were.
I learned quite a bit (tie-ing, platform independent filesystem access, etc) by reading the code for File::chdir. It is also a very handy module to use in your scripts, I use it all the time.
I would also add to bvr's list: read the source for modules that you use frequently, since you are already familiar with their expected behavior, you can more clearly see what is being done to achieve that result.
The question is what you want to learn, but it is certainly good idea to study various modules, because you learn to read other people code and learn various tricks. Some random recommendations I can think of
start with smaller modules with clear interface you know and are interested in
once you feel familiar with organization of modules and basics, try something larger
try rather newer modules
look into test suite and into examples
if you don't understand specific piece, try to make reduced example a play with it
It is hard to recommend something specific, but I liked my recent look into Web::Scraper module.
If you're fluent in perl - if don't perldoc ;) - , sugest learn the packages Task::Kensho or Modern::Perl.
These packages do cover comprehensive in culture Perl, since tests until hacks, passing by crawling, modules to developers, e-mail, dates, modern oriented obejct in Perl.
Participe of discussion lists, read the history of list, irc.
Perl have many tricks, the community always responds with enthusiasm =)
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Closed 12 years ago.
I love Ruby and have been using it for a few years to handle day-to-day scripting tasks. Lately however, I've had a number of people tell me that Perl is where it's at. I have nothing against Perl, but it seems like it's kind of fallen behind the times a bit.
However, that's probably just my perception, so I'm asking all of you, what makes Perl so great? I'm genuinely seeking information here; I'd like to understand why this language has such ardent followers.
I know a good handful of hackers who left Perl to go to Ruby. Python is obviously a nice language too. I am neither saying nor implying anything against either.
Pros for Perl 5
Since about 2005 or so Perl has been in a fairly dramatic renaissance in both CPAN and core releases. Perl 6 has helped drive this by sending concepts like role-oriented OO back. Strawberry Perl has made Perl hacking on Windows more like *nix.
The CPAN is huge, still growing, and most of the more widely used authors/teams are responsive to bugfixes. Most popular Perl modules are tested widely and well. CPAN testers recently sent their 10 millionth test report.
Many of the big kits have good communities associated where expert help is available quickly.
The tool chain has become very flexible.
The combination of perlbrew, local::lib, and cpanminus lets users (even without root) have an arbitrary number of perl versions and libraries accessible on the same box.
Many of things that Java, Ruby, Python do right come back to Perl and with facility. For example–
KinoSearch is Lucene but even faster by some benchmarks.
Catalyst is Rails but more flexible. It’s a completely agnostic C with regards to the M and V.
Plack is Python’s WSGI + Ruby’s Rack.
It’s as fast and personal or readable and robust as you want it to be.
A short one-liner can edit every HTML file in your tree when you’re in a hurry to fix something.
A clear and robust program with error reporting, logging, and feedback built on any of the 6 or 7 suitable HTML/XML packages could do the same for a client.
Perlmonks. Though there are notable exceptions, the Perl community is generally friendly, helpful, and positive.
There are quite a few good Perl jobs waiting to be filled. The back and forth between the high level languages has left oodles of Perl in the wild without a matching crop of Perl-centric devs. (I get 5-7 cold calls from recruiters a year.)
It’s fun. In quotes: “Perl has the happiest users.” I can’t speak to the scientific nature of that but I can say I only program today because Perl exists. Many other Perl hackers share this stupid giddiness for the language.
Keep in mind it’s not a zero sum game. The more languages you can wield, the better.
If I had to name one great strength of Perl, it's one word: CPAN.
Having worked with Ruby as well, I'd not say that Perl is necessarily better or worse, but definitely more mature. It is, after all, much older. However, it's not decrepit. It has plenty of modern stuff, e.g., Moose and the 5.10 and 5.12 updates have fixed a lot of problems that the ancient 5.0.x had.
(And if you're wondering: Perl 5 and Perl 6 are different languages. The similar name is an unfortunate mistake. Though Perl 5 does borrow ideas from Perl 6 and vice versa.)
CPAN.
The syntax of Perl is sometimes painful to look at but it is available on Unix machines everywhere and with the command line access to the huge number of packages in CPAN (which can also be accessed via browser), Perl is the de facto standard because of its broad applicability and availability.
These days, IMO the main reason to use Perl is that you can be pretty confident that just about any UNIX system will have it available, even on the sparser commercial UNIX distros.
Also, it has some features that make it work very conveniently with the UNIX shell and filesystem. Perl one-liners are convenient in shell scripting when you need a little more power.
If you're not on a UNIX machine then there's probably little advantage over more modern scripting languages.
First of all I love Python and Ruby as well. In fact I think anything you can do in anyone of the 3 languages you can do in the other just as easily.
CPAN however is a big advantage. There are not many times I find myself looking for a specific general functionality and not finding a module for it.
The greatest thing for me is however is that I can do absolutely everything I want, quickly, and in 10 different ways if I like, but maybe that's just because Perl is my 'mother tongue'.
Anyway, I think it depends on what you want to do. If you want to create a scalable website or web application with all the plumbing (authentication, authorization, session tracking, database ORM, etc, etc) taken care of, it can be done in Perl, but the hassle is not worth it. Go with Python (Django) or Ruby (Rails 3.0 rocks) then.
Good luck and watch out fire setting of flamewars with this subject, this kind of stuff get seriously get you hurt ;)
Rob
I have inherited a broad, ill-designed web portfolio at my job. Most pages are written in Perl as most of the data ingested, processed, and displayed on the site comes in the form of flat-files which then have to be meticulously regexed and databased in our MySQL and Oracle databases.
As the first IT-trained manager of this environment, I am taking it upon myself to scrub the websites and lay down some structure to the development process. One of the choices I have been given is to choose whether or not to continue in Perl. There is substantial in-house talent for Java and PHP is rather easy to learn. I have considered taking the reins off the developers and letting them choose whatever language they want to use for their pages but that sounds like it might be trouble if the guy who chose PHP gets hit by a bus and no one else can fix it.
As the years go by hiring Perl programmers becomes more and more difficult and the complexity of maintaining legacy Perl code from previous developers whose main focus may have been just getting a page up and running is becoming very resource-consuming. Another, previous (non-IT) manager was more focused in on quick turnaround and immediate gratification of pages rather than ensuring that it was done right the first time (he has since been promoted outside our branch).
The production server is solaris. MySQL has most of our data but new projects have begun using Oracle more and more (for GIS data). Web servers are universally Apache. We live in an intranet disconnected from the regular internet. Our development is conducted in an Agile, iterative manner.
Whatever language is chosen to push forward into, there are resources to have the existing development staff re-trained. No matter what, the data that comes into our environment will have to be regexed to death so perl isn't going away anytime soon. My question to the community is, what are the pros and cons of the following languages for the above-defined web dev environment: Perl, PHP, Java, Python, and --insert your favorite language here--. If you had it to do all over again, which language set-up would you have chosen?
Edits and Clarifications:
Let me clarify a bit on my original post. I'm not throwing everything away. I've been given the opportunity to adjust the course of the ship to what I believe is a better heading. Even if I chose a new language, the perl code will be around for some time to come.
Hypothetically speaking, if I chose Assembly as my new language (haha) I would have to get the old developers up to speed probably by sending them to some basic assembly classes. New pages/projects would be in the new language and the old pages/projects would have to play nice with the new pages/projects. Some might one day be rewritten into the new language, some may never be changed.
What will likely always be in Perl will be the parsing scripts we wrote years ago to sift through and database information from the flat files. But that's okay because they don't interface with the webpages, they interface with the database.
Thank you all for your input, it has been very very helpful thus far.
It seems that your problem is more legacy code and informal development methodology than the language per se. So if you already have Perl developers on staff, why not start modernizing your methods and your code base, instead of switching to a new language, and creating an heterogeneous code base.
Modern Perl offers a lot in terms of good practices and powerful tools: testing is emphasized, with the Test::* modules and WWW::Mechanize, data base interaction can be done through plain DBI, but also using ORM modules like the excellent DBIx::Class, OO with Moose is now on par with more modern languages, mod_perl gives you access to a lot of power within Apache. There are also quite a few MVC frameworks for Perl. One that's getting a lot of attention is Catalyst.
Invest in a few copies of Perl Best Practices, bring in a proper trainer for a few classes on modern development methods, and start changing the culture of your group.
And if you have trouble finding developers that are already proficient in Perl, you can always hire good PHP people and train them, that shouldn't be too difficult. At least their willingness to learn a new language would be a good sign of their flexibility and will to improve.
It is always tempting to blame the state of your code on the language its written in, but in your case I am not sure that is the case. Lots of big companies seem to have no problem managing huge code bases in Perl, the list is long but the main Web companies are all there, along with a number of financial institutions.
I would bring in someone who is very good at Perl, to at least look at the current design. They would be able to tell you how bad the Perl code really is, and what needs to be done to get it into good shape.
At that point I would start considering my options. If the Perl code is salvageable, well than great, hire someone proficient in Perl. Also train some of your existing staff to help on the existing code-base. If you don't have someone proficient in Perl in charge of the Perl code, your code-base may become even worse than it already is.
Only if it was in terrible shape, would I consider abandoning it for another language. What that language is, that is something your going to have to think about that yourself.
p.s. I'm a bit biased, I prefer Perl
If regex is important I would choose a language with good support.
If you would use java, you will not be able to just copy paste your regex code from the perl code because the slashes have to be escaped. So I would vote against java.
I'm not familiar with php enough to know its regex features, but given your choices I would go for python. You can create cleaner code in python.
Would ruby also be an option? It also has good perl like regex support and rails supports agile web development out of the box.
first off let me point out that MySQL's spatial extensions work with GIS.
Second, if you have a bunch of Perl programmers that will need tow ork on the new sites then your best bet is to choose something they won't have too much trouble understanding. The obvious "something" there is PHP. When I learnt PHP I'd done some Perl years ago and picked up PHP in no time at all.
Switching to something like Java or .Net (or even Ruby on Rails) would be a far more dramatic shift in design.
Plus with Apache servers you already have your environment set up and you can probably stage any development as a mix of Perl and PHP reasonably easily.
As to the last part of your question: what would you do it in if you could do it over again? To me that's a seprate and basically irrelevant question. The fact is you're not rewinding and starting over, you're just... starting over. So legacy support, transition, skills development and all those other issues are far more important than any hypothetical question of what you'd choose in a perfect world if all other things were equal.
Love it or hate it, PHP is popular and is going nowhere anytime soon. Finding skiled people to do it is not too difficult (well, the dificulty is filtering them out from the self-taught cowboy script jockeys who think they can code but can't) and it's not a far step from Web-based Perl.
If your developers are any good, they'll be able to handle anything thrown at them. Deciding what language to use is quite a tricky strategic position, but I recommend you think very carefully before introducing any MORE (i.e. don't).
Unless of course, there is something that you absolutely cannot do (or cannot do sanely) with what you've got.
I think choosing a single language is key and if your database is primarily MySQL, then PHP seems like the obvious choice. It naturally works with your database, it's open source and there is tons of documentation, source code, doesn't require compiling, etc.
People come and go through positions and any website will evolve over time. If you have the ability to set some guidelines and rules, I would choose something that is forgiving, common-place, and easy(er) to learn.
I'd also suggest writing it down so people in the future don't re-invent the wheel.
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I've started learning Perl but most of my former programming experience has been in languages that emphasize object oriented programming such as C# and Java. All the Perl examples I have found tend to be long single function programs and I find my self writing code the same way. Are there any resources or tutorials for writing maintainable well structured programs?
Firstly, regardless of what sort of Perl programming you're doing, you'll probably find Perl::Critic to be invaluable. The command-line tool is by far the most convenient for getting feedback on your code, but you there is also a web interface where you can upload your Perl code and receive instant, automated feedback. Note that Perl::Critic isn't going to teach you good structure, but it will help improve your style in general, and steer you away from some common mistakes.
To go with Perl::Critic, I'd recommend getting a copy of Perl Best Practices (PBP). It contains a lot of detailed information upon which Perl::Critic was based. Even if you disagree with particular guidelines in the book, it makes you think about how you code, and that's very, very valuable. You don't have to shell out money for a book, but the two compliment each other very nicely, and there are lengthy discussions you'll find in PBP that you won't get from Perl::Critic.
If you've already worked with other OO languages and OO design, the you'll probably find Moose to be a comfortable transition. Moose is very stable, very well supported, and has a huge and active community (especially via IRC). Moose supersedes almost all the existing OO Perl advice out there, including my own. Object Oriented design is common for a reason; it makes sense for a lot of projects, and there's no reason not to use it in Perl.
Personally, I found a massive improvement in my own program structure when I moved to a test-driven development model. Under such a model, breaking a problem down into small, easily tested units is essential. Start with Test::Tutorial if you're new to testing in Perl and then look at some other testing resources or books if you want to learn more. Use a tool like Devel::Cover or Devel::NYTProf to see what your test cases are hitting and what they're not. Having code that's hard to test is often a sign of poor structure.
Having said all this, the best teacher by far is to get involved with an existing Perl project with experienced contributors. See how they do things, and when you make contributions, think about their advice. If you want a real application with awesome cool value that seems to have sucked up the very best and brightest of the Perl community, then I'd recommend getting involved with Padre, the Perl editor.
If (for whatever reason) you can't get involved with another project, then consider posting code samples to communities such as Stack Overflow, or PerlMonks. Better still, if you can make your code open source, then do so, and solicit feedback. All programming languages are better learnt with others who are already familiar with them, and Perl is no exception here.
May you do Good Magic with Perl,
Paul
Perl Best Practices
If you're learning OO Perl you might as well move on to the next big thing and start learning Moose.
Moose is a postmodern object system for Perl 5 that takes the tedium out of writing object-oriented Perl. It borrows all the best features from Perl 6, CLOS (Lisp), Smalltalk, Java, BETA, OCaml, Ruby and more, while still keeping true to its Perl 5 roots.
Moose is 100% production ready and in heavy use in a number of systems and growing every day.
If you already know how to write well-structured programs and you want to write well-structured Perl, but the only impediment to that is the abundance of ancient, crufty, spaghetti-code examples that are scattered around the net and refuse to die...
Ignore the examples. Or at least ignore their poor structure and only pay attention to the small syntactic bits that you need to learn from.
There is nothing in Perl that pushes you to write bad code. If you already know how to write good code in other languages, then you can apply the exact same principles and practices in Perl. It's merely a matter of discipline, just like in any other language.
If you feel you already are learning the basics and want to improve program structure, then I'd suggest these books, probably best to read in this order:
Intermediate Perl -- this is probably the place to start for what you're asking about; covers developing and using Perl modules (essential for good structure), references, complex data structures, OO, and more
Perl Medic: Transforming Legacy Code -- demonstrates well-structured Perl by showing how to fix poorly-structured Perl
Effective Perl Programming: Writing Better Programs with Perl -- a classic, but still useful; full of Perl idioms that will help you write more Perl-ish Perl; not much on OO, but covers more fundamental coding structures to make your code more succinct and yet more expressive. I think of this as the book that got me from Perl literacy to Perl fluency
All three are best once you've comfortable with basic Perl syntax, but none of them get too far into esoteric advanced concepts that you can't follow if you're still starting out in Perl but have reasonable programming experience in other languages already.
Apart from the sources mentioned above I strongly recommend the book
"Higher-Order Perl" by Mark Jason Dominus.
If you can afford it buy it, otherwise the author has put the book on his website for free as in free beer, Free Higher Order Perl. For the PDF version: direct download URL (1.9 MB).
Edit:
I forgot to mention Perl Design Patterns. The PerlDesignPatterns site is a very good resource or reference for learning Perl design patterns.
Object-Oriented Perl
http://perl.about.com/od/objectorientedperl/Object_Oriented_Perl.htm
http://www.codeproject.com/KB/perl/camel_poop.aspx
http://www.tutorialspoint.com/perl/perl_oo_perl.htm
Personally, I didn't write good OO Perl until I started learning Java. I recommend you spend a small amount of time learning OO in a true OO language and apply what you learn to Perl.
For a place to be mentored, PerlMonks is GREAT.
Write Perl the way you would write C, although you should take advantage of some things BEGIN blocks and modules. It should be formatted so that it looks more or less like old style K&R C code.
As for structure, skip the OO stuff and style it as ADTs instead:
http://en.wikipedia.org/wiki/Abstract_data_type
Basically you do this by using data-structures where you would have used objects in OO (and separating out the algorithms into their own functions).
Then, pick only one way to do things and stick to it, consistency is vital to readability.
If you manage that, the code can be both readable and easy to understand.
Paul.