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diff --git a/pod/perlfaq1.pod b/pod/perlfaq1.pod new file mode 100644 index 0000000000..2510a4b1f1 --- /dev/null +++ b/pod/perlfaq1.pod @@ -0,0 +1,248 @@ +=head1 NAME + +perlfaq1 - General Questions About Perl ($Revision: 1.10 $) + +=head1 DESCRIPTION + +This section of the FAQ answers very general, high-level questions +about Perl. + +=head2 What is Perl? + +Perl is a high-level programming language with an eclectic heritage +written by Larry Wall and a cast of thousands. It derives from the +ubiquitous C programming language and to a lesser extent from sed, +awk, the Unix shell, and at least a dozen other tools and languages. +Perl's process, file, and text manipulation facilities make it +particularly well-suited for tasks involving quick prototyping, system +utilities, software tools, system management tasks, database access, +graphical programming, networking, and world wide web programming. +These strengths make it especially popular with system administrators +and CGI script authors, but mathematicians, geneticists, journalists, +and even managers also use Perl. Maybe you should, too. + +=head2 Who supports Perl? Who develops it? Why is it free? + +The original culture of the pre-populist Internet and the deeply-held +beliefs of Perl's author, Larry Wall, gave rise to the free and open +distribution policy of perl. Perl is supported by its users. The +core, the standard Perl library, the optional modules, and the +documentation you're reading now were all written by volunteers. See +the personal note at the end of the README file in the perl source +distribution for more details. + +In particular, the core development team (known as the Perl +Porters) are a rag-tag band of highly altruistic individuals +committed to producing better software for free than you +could hope to purchase for money. You may snoop on pending +developments via news://genetics.upenn.edu/perl.porters-gw/ and +http://www.frii.com/~gnat/perl/porters/summary.html. + +While the GNU project includes Perl in its distributions, there's no +such thing as "GNU Perl". Perl is not produced nor maintained by the +Free Software Foundation. Perl's licensing terms are also more open +than GNU software's tend to be. + +You can get commercial support of Perl if you wish, although for most +users the informal support will more than suffice. See the answer to +"Where can I buy a commercial version of perl?" for more information. + +=head2 Which version of Perl should I use? + +You should definitely use version 5. Version 4 is old, limited, and +no longer maintained. Its last patch (4.036) was in 1992. The last +production release was 5.003, and the current experimental release for +those at the bleeding edge (as of 27/03/97) is 5.003_92, considered a beta +for production release 5.004, which will probably be out by the time +you read this. Further references to the Perl language in this document +refer to the current production release unless otherwise specified. + +=head2 What are perl4 and perl5? + +Perl4 and perl5 are informal names for different versions of the Perl +programming language. It's easier to say "perl5" than it is to say +"the 5(.004) release of Perl", but some people have interpreted this +to mean there's a language called "perl5", which isn't the case. +Perl5 is merely the popular name for the fifth major release (October 1994), +while perl4 was the fourth major release (March 1991). There was also a +perl1 (in January 1988), a perl2 (June 1988), and a perl3 (October 1989). + +The 5.0 release is, essentially, a complete rewrite of the perl source +code from the ground up. It has been modularized, object-oriented, +tweaked, trimmed, and optimized until it almost doesn't look like the +old code. However, the interface is mostly the same, and compatibility +with previous releases is very high. + +To avoid the "what language is perl5?" confusion, some people prefer to +simply use "perl" to refer to the latest version of perl and avoid using +"perl5" altogether. It's not really that big a deal, though. + +=head2 How stable is Perl? + +Production releases, which incorporate bug fixes and new functionality, +are widely tested before release. Since the 5.000 release, we have +averaged only about one production release per year. + +Larry and the Perl development team occasionally make changes to the +internal core of the language, but all possible efforts are made toward +backward compatibility. While not quite all perl4 scripts run flawlessly +under perl5, an update to perl should nearly never invalidate a program +written for an earlier version of perl (barring accidental bug fixes +and the rare new keyword). + +=head2 Is Perl difficult to learn? + +Perl is easy to start learning -- and easy to keep learning. It looks +like most programming languages you're likely to have had experience +with, so if you've ever written an C program, an awk script, a shell +script, or even an Excel macro, you're already part way there. + +Most tasks only require a small subset of the Perl language. One of +the guiding mottos for Perl development is "there's more than one way +to do it" (TMTOWTDI, sometimes pronounced "tim toady"). Perl's +learning curve is therefore shallow (easy to learn) and long (there's +a whole lot you can do if you really want). + +Finally, Perl is (frequently) an interpreted language. This means +that you can write your programs and test them without an intermediate +compilation step, allowing you to experiment and test/debug quickly +and easily. This ease of experimentation flattens the learning curve +even more. + +Things that make Perl easier to learn: Unix experience, almost any kind +of programming experience, an understanding of regular expressions, and +the ability to understand other people's code. If there's something you +need to do, then it's probably already been done, and a working example is +usually available for free. Don't forget the new perl modules, either. +They're discussed in Part 3 of this FAQ, along with the CPAN, which is +discussed in Part 2. + +=head2 How does Perl compare with other languages like Java, Python, REXX, Scheme, or Tcl? + +Favorably in some areas, unfavorably in others. Precisely which areas +are good and bad is often a personal choice, so asking this question +on Usenet runs a strong risk of starting an unproductive Holy War. + +Probably the best thing to do is try to write equivalent code to do a +set of tasks. These languages have their own newsgroups in which you +can learn about (but hopefully not argue about) them. + +=head2 Can I do [task] in Perl? + +Perl is flexible and extensible enough for you to use on almost any +task, from one-line file-processing tasks to complex systems. For +many people, Perl serves as a great replacement for shell scripting. +For others, it serves as a convenient, high-level replacement for most +of what they'd program in low-level languages like C or C++. It's +ultimately up to you (and possibly your management ...) which tasks +you'll use Perl for and which you won't. + +If you have a library that provides an API, you can make any component +of it available as just another Perl function or variable using a Perl +extension written in C or C++ and dynamically linked into your main +perl interpreter. You can also go the other direction, and write your +main program in C or C++, and then link in some Perl code on the fly, +to create a powerful application. + +That said, there will always be small, focused, special-purpose +languages dedicated to a specific problem domain that are simply more +convenient for certain kinds of problems. Perl tries to be all things +to all people, but nothing special to anyone. Examples of specialized +languages that come to mind include prolog and matlab. + +=head2 When shouldn't I program in Perl? + +When your manager forbids it -- but do consider replacing them :-). + +Actually, one good reason is when you already have an existing +application written in another language that's all done (and done +well), or you have an application language specifically designed for a +certain task (e.g. prolog, make). + +For various reasons, Perl is probably not well-suited for real-time +embedded systems, low-level operating systems development work like +device drivers or context-switching code, complex multithreaded +shared-memory applications, or extremely large applications. You'll +notice that perl is not itself written in Perl. + +The new native-code compiler for Perl may reduce the limitations given +in the previous statement to some degree, but understand that Perl +remains fundamentally a dynamically typed language, and not a +statically typed one. You certainly won't be chastized if you don't +trust nuclear-plant or brain-surgery monitoring code to it. And +Larry will sleep easier, too -- Wall Street programs not +withstanding. :-) + +=head2 What's the difference between "perl" and "Perl"? + +One bit. Oh, you weren't talking ASCII? :-) Larry now uses "Perl" to +signify the language proper and "perl" the implementation of it, +i.e. the current interpreter. Hence Tom's quip that "Nothing but perl +can parse Perl." You may or may not choose to follow this usage. For +example, parallelism means "awk and perl" and "Python and Perl" look +ok, while "awk and Perl" and "Python and perl" do not. + +=head2 Is it a Perl program or a Perl script? + +It doesn't matter. + +In "standard terminology" a I<program> has been compiled to physical +machine code once, and can then be be run multiple times, whereas a +I<script> must be translated by a program each time it's used. Perl +programs, however, are usually neither strictly compiled nor strictly +interpreted. They can be compiled to a bytecode form (something of a Perl +virtual machine) or to completely different languages, like C or assembly +language. You can't tell just by looking whether the source is destined +for a pure interpreter, a parse-tree interpreter, a byte-code interpreter, +or a native-code compiler, so it's hard to give a definitive answer here. + +=head2 What is a JAPH? + +These are the "just another perl hacker" signatures that some people +sign their postings with. About 100 of the of the earlier ones are +available from http://www.perl.com/CPAN/misc/japh . + +=head2 Where can I get a list of Larry Wall witticisms? + +Over a hundred quips by Larry, from postings of his or source code, +can be found at http://www.perl.com/CPAN/misc/lwall-quotes . + +=head2 How can I convince my sysadmin/supervisor/employees to use version (5/5.004/Perl instead of some other language)? + +If your manager or employees are wary of unsupported software, or +software which doesn't officially ship with your Operating System, you +might try to appeal to their self-interest. If programmers can be +more productive using and utilizing Perl constructs, functionality, +simplicity, and power, then the typical manager/supervisor/employee +may be persuaded. Regarding using Perl in general, it's also +sometimes helpful to point out that delivery times may be reduced +using Perl, as compared to other languages. + +If you have a project which has a bottleneck, especially in terms of +translation, or testing, Perl almost certainly will provide a viable, +and quick solution. In conjunction with any persuasion effort, you +should not fail to point out that Perl is used, quite extensively, and +with extremely reliable and valuable results, at many large computer +software and/or hardware companies throughout the world. In fact, +many Unix vendors now ship Perl by default, and support is usually +just a news-posting away, if you can't find the answer in the +I<comprehensive> documentation, including this FAQ. + +If you face reluctance to upgrading from an older version of perl, +then point out that version 4 is utterly unmaintained and unsupported +by the Perl Development Team. Another big sell for Perl5 is the large +number of modules and extensions which greatly reduce development time +for any given task. Also mention that the difference between version +4 and version 5 of Perl is like the difference between awk and C++. +(Well, ok, maybe not quite that distinct, but you get the idea.) If +you want support and a reasonable guarantee that what you're +developing will continue to work in the future, then you have to run +the supported version. That probably means running the 5.004 release, +although 5.003 isn't that bad (it's just one year and one release +behind). Several important bugs were fixed from the 5.000 through +5.002 versions, though, so try upgrading past them if possible. + +=head1 AUTHOR AND COPYRIGHT + +Copyright (c) 1997 Tom Christiansen and Nathan Torkington. +All rights reserved. See L<perlfaq> for distribution information. |