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Where is a good place to learn how to use CGI with perl for making websites?
I will be running on Linux with apache2, but there is a possibility I may run on Windows for our company. I need to make a site for internal use only, that one might run on Windows with IIS.
If you’re not forced into CGI, forget about it – it’s obsolete & sucks. Some alternatives are listed in this related question.
The CGI module from CPAN is the canonical starting point for basic CGI scripts, and there are a lot of reasons to use it versus handling your own param parsing. CGI.pm (the module) handles behind the scenes a lot of things that you don't want to have to build yourself. If you need to maintain state, CGI::Session helps. And if you plan on expanding beyond simple CGI scripting you can plan larger applications around CGI::Application in combination with a templating solution.
For the output side, Template::Toolkit or HTML::Template are commonly used.
There is the somewhat outdated book, CGI Programming with Perl (O'Reilly). Though it is outdated it does give a good overview and starting point for basic CGI. I wouldn't hesitate to recommend purchasing a used copy (there are copies available used online starting for the cost of shipping). It's definitely worth reading through. Even though it doesn't address some of the more modern issues such as Unicode, it still lays out for you the start to finish CGI process. That alone is worth the read.
Perhaps start by reading the POD for CGI, and later for CGI::Session. Build from there.
There is so much more to the "state of the art" nowadays than simple CGI, but you have to start somewhere. If your plan is to develop complex sites, beyond what CGI::Application can facilitate, you'll start wondering about Catalyst, Mojolicious, and other frameworks. But that's a different topic. The old saying from Economists, "It depends..." It depends on what you want to accomplish, whether CGI will be a good fit versus a more robust and scalable framework.
If you can, forget CGI.
curl -L http://cpanmin.us | perl - --sudo App::cpanminus
cpanm --interactive Task::Plack
will run a while (bit long), but will install for you the basics for modern perl/web development - Plack and several middle-wares.
Read step-by-step thru fantastic Miyagawa's Plack advent calendar, and after a while you will be an perl/web/app-dev/guru. ;)
Module CGI will fill your CGI needs. As for making web sites, that has nothing to do with CGI, and I don't have a reference handy.
Where is a good place to learn how to
use CGI with perl for making websites?
I suggest a good history book that talks about the "dot-com boom" of the mid to late 90s - that's about the time period when CGI was in common use.
If, on the other hand, you'd like to learn something that's still relevant today, I suggest looking at mod_perl or FastCGI, using a framework such as Catalyst or Plack.
Please don't learn CGI. Learn instead a modern and clean Perl web engine such as Dancer or Mojolicious. And if you want to understand the lower levels of the modern Perl 5 stack, read about PSGI.
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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 am new to developing a website using Perl CGI scripts.
What are the prerequisites for Perl?
Please give me some basic ideas or some good tutorials.
Do you mean: what prerequisite knowledge would help you learn Perl?
The Perl language grew out of the best features of the Unix commands grep, awk, sed, and shell scripts, plus some C. If you are strong in those areas, Perl will seem like a good fit. You'd already be used to cryptic variable names, quick-n-dirty looping constructs, dynamic typing, regular expressions, and standard input/output.
First decide if you are writing a CGI script or an Apache handler. The 2 are coded completely differently, but both have their advantages and disadvantages.
If you want to run your script using CGI (or FCGI), I recommend this tutorial for beginning programmers. It will help you through creating simple forms. If you already know a bit about programming a script language, you will be able to skim-read a lot of that. If you are a new programmer, you might also want zo look up a few alternatives, like coding CGI scripts with Python, a language often thought to be better suited to new programmers.
I would point you towards learn.perl.org, the Modern Perl book by chromatic, and the overview of web frameworks on the Perl 5 wiki. Also make sure that the tutorials and articles you use are relatively recent. Perl has been around for a long time and modern Perl is different from what people wrote 10 years ago.
I suggest starting with PSGI. It is somewhat new (compared to mod_perl), but it's Perl's answer to Python WSGI. Most of the large frameworks support it, as does other interesting projects like Starman. I would start there and Google anything I don't understand.
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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.
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I am a bioinformatics student and am in the process of learning perl. I don't have a strong programming background but would like for that to change.
Right now I am in the process of reading/following and coding from this book
I want to know is this the best way to go about learning perl? Should I be experimenting with regular expressions more? Should I keep trying writing sample perl scripts?
Related: what are good books for learning perl
The definitive learning Perl book is aptly called "Learning Perl". Get it.
I cannot recommend writing sample scripts. Try to write something that you need. It doesn't have to be a big endeavor; everyone needs a little tool now and then. Writing sample scripts is boring; always was, always will be.
This seems like a potential duplicate as here are some related questions:
What are the best resources to starting learning Perl?
What’s the best online source to learn Perl?
Like most other answers on this post I can't disagree with the choice of "Learning Perl" as your first Perl text. Keep a copy of the perldoc documentation available for quick reference(I prefer using the html/pdf format which is available as a download from the main page).
In order to keep things from getting boring, especially in the initial stages I started converting my shell scripts to Perl, hacking away at it until I had three or more different versions of the same program with decreasing file size(not great for maintenance though). But then you know what they say - TMTOWTDI. Now I don't bother with shell scripts any more, writing it in Perl results in smaller turnaround times and the code can be easily reused and enhanced.
Once you are familiar with the more advanced concepts and are approaching a level of comfortability with using it for your day-to-day work or just simple one-liners you might want to have a look at Mark Jason Dominus' Higher-Order Perl which, according to me, takes the language and the reader's understanding of it to an entirely new level. The chapter on "Recursion and Callbacks" was a real eye-opener and changed my style completely from that of writing C-programs in Perl to actually writing "Perl" programs in Perl.
I use the online book "Learning Perl the Hard Way" to teach my coworkers about Perl.
Don't be intimidated by the title, it's just that it's directed at programmers who are already fluent in another language and therefore it doesn't focus on the programming part, but mostly on the Perl part, so it may apply better to your case (or not).
You really can't go wrong with the Lama book
Learning Perl
There's quite a library of O'Reilly books on Perl. Programming Perl is also excellent and probably worth having to complement the Lama book - I have both on my shelves and although I haven't needed to code in Perl for quite some time I found these books together a solid enough combination. The Perl Cookbook came in useful too (yes, this is one of those areas that O'Reilly has pretty much sew up :-).
As to practical exercises, Perl does have something of a reputation as a 'Write Only' language, so look for clear examples and if you are confused by anything don't necessarily assume that the problem is you - there's always more than one way to do it.
You also might want to look for examples of good code to study.
My experience is that there's nothing better for learning than doing. But you need someone to provide feedback, especially when you hit roadblocks that you can't get past. Stackoverflow is good for that, but, IME, Perlmonks is better in that there is a chatterbox for immediate feedback, as well as their question-and-answer posts for longer questions, combined with a more specialised environment. (And Larry Wall has been rumoured to hang out there, too, as well as a number of the authors of the above-referred-to books.)
Learn by doing. Get the books mentioned by others, but the real way to learn is to start a simple project. Mine was a Gtk based SQL editor. If you run into problems ask questions here and on the Perl Beginners list.
The choice of book is can be vary from person to person. So, as bioinformatics student who use perl, don't get any book that called "(X Programming language) for bioinformatics". Usually this kind of book is either.
They only give very basic of that programming language. You gonna to miss all the power from that language.
Wasting its space on how to use API, which you can find information easily via google.
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Can you suggest some good MVC framework for perl -- one I am aware of is catalyst
The need is to be able to expose services on the perl infrastructure which can be called by Java/.Net applications seamlessly.
I'll tell you right now that Catalyst has by far the best reputation amongst Perl developers in terms of a rapid application development MVC framework.
In terms of "pure" MVC I'm not sure there are even that many "mature" or at least production-ready alternatives.
If Catalyst doesn't seem right to you, then you could build upon the lightweight framework CGI::Application to suit your needs or take a look at some of the lesser known MVC frameworks like PageKit and Maypole.
Since this old thread popped up, I will mention two exciting new additions to the Perl MVC world:
Dancer (CPAN) which is heavily influenced by Ruby's Sinatra, known for being very lightweight
Mojolicious (CPAN) which is written by the original developer of Catalyst to use what he learned there, it has no non-core dependencies, with very modern builtins (HTML5/CSS3/Websockets, JSON/XML parsers, its own UserAgent/templating engine)
(N.B. I have used Mojolicious more than Dancer, and as such if I missed some features of Dancer that I listed for Mojolicious then I apologize in advance)
Another alternative besides the ones already mentioned is Continuity; however, it is (as the name is meant to imply) continuation-based rather than MVC in the typical sense. Still, it’s worth mentioning because it is one of the better Perl web frameworks.
That said, I like Catalyst much better than any of the alternatives. And it’s still getting better all the time! The downside of that is that current preferred coding approaches continue to evolve at a fairly hurried clip – but for the last couple of versions, there has been strong emphasis on API compatibility, so the burden is now mostly mental rather than administrative. The upcoming port of the internals to Moose in particular is poised to provide some excellent benefits.
But the biggest argument in favour of Catalyst, IMO, is the Chained dispatch type. I have seen nothing like it in all of web-framework-dom, and it is a most excellent tool to keep your code as DRY as possible. This couples well with another great thing that Catalyst provides, namely uri_for – a method which takes a controller and a bunch of arguments and then constructs a URI that would dispatch to that place, which it returns. Together, these facilities mean that you can structure your URI space any way you deem right, yet at the same time can structure your controllers to avoid duplication of logic, and keep templates independent of the URI structure.
It’s just brilliant.
Seconding comments made by others: Catalyst (which more or less forked from Maypole) is by far and away the most complete and robust of them. There is a book by Jonathan Rockway that will certainly help you come to grips with it.
In addition to the 'Chained' dispatch type, the :Regex (and :LocalRegex) dispatch methods provide enormous flexibility. The latest app we've built here supports a lot of disparate-looking URLs through just a handful of subs using :LocalRegex.
I also particularly like the fact that you are not limited to a particular templating language or database. The mailing list (and the book) both have a preference for Template::Toolkit (as do I), and DBIx::Class (we continue to use Class::DBI), but you can use pretty much anything you like. Catalyst is marvelously agnostic that way.
Don't be put off by the fact Catalyst seems to require half of CPAN as dependencies. Once you get it up and running, it is a well-oiled machine. It has reached a level of maturity now that once you come to grips with it, you find it 'fades into the background'. You spend your time solving business needs, not fighting with the tools you use.
It does what it says on the tin. Catalyst++
Been playing with Squatting the last few days and I have to say it looks very promising and been fun to use.
Its a micro webframework (or web microframework ;-) and is heavily influenced by Camping which is written in Ruby.
NB. Squatting (& Camping) don't have model components baked into the framework. Here's the authors comments on models... "Models? The whole world is your model. ;-) I've always been ambivalent about defining policy here. Use whatever works for you"
There is also CGI::Application, which is more like the guts of a framework. It helps a person to write basic CGI's and glue bits on to it to make it as custom as they like. So you can have it use hardly any modules, or just about everyone under the sun.
Catalyst is the way to go. There is also Jifty, but (last time I looked), it had terrible documentation.
If you are already aware of Catalyst, then I recommend focusing on it. It is mature, well-documented, and has a very large user-base, community, and collection of plug-ins.
For your problem I would take a look into Jifty::Plugin::REST which allows access to models and actions using various formats.
Let me just say that Jifty doesn't have terrible documentation. However, most of included documentation is API documentation, but there is very low-noise mailing list which has useful tips and links to applications.
Wiki at http://jifty.org/ is another resource which has useful bits.
If your goal is to make video store (my favorite benchmark for 4GLs and CRUD frameworks) in afternoon, it's really worth a look!
Another options is Gantry when used in conjunction with the BigTop module it can reduce the time it takes to build simple CRUD sites.
There is also Clearpress which I can recommend as a useful database backed application. It needs fewer dependencies than Catalyst. We have written a few large applications with it, and I run a badminton ladder website using it.
I have built some applications with Kelp, it's easy to learn and very helpful.