FAQsGeneral Questions About PerlDaftar Isi NAMEperlfaq1 - General Questions About Perl DESCRIPTIONThis section of the FAQ answers very general, high-level questionsabout Perl. What is Perl?Perl is a high-level programming language with an eclectic heritagewritten by Larry Wall and a cast of thousands. Perl's process, file, and text manipulation facilities make itparticularly well-suited for tasks involving quick prototyping, systemutilities, software tools, system management tasks, database access,graphical programming, networking, and web programming. Perl derives from the ubiquitous C programming language and to alesser extent from sed, awk, the Unix shell, and many other toolsand languages. These strengths make it especially popular with web developersand system administrators. Mathematicians, geneticists, journalists,managers and many other people also use Perl. Who supports Perl? Who develops it? Why is it free?The original culture of the pre-populist Internet and the deeply-heldbeliefs of Perl's author, Larry Wall, gave rise to the free and opendistribution policy of Perl. Perl is supported by its users. Thecore, the standard Perl library, the optional modules, and thedocumentation you're reading now were all written by volunteers. The core development team (known as the Perl Porters)are a group of highly altruistic individuals committed toproducing better software for free than you could hope to purchase formoney. You may snoop on pending developments via thearchivesor read the faq,or you can subscribe to the mailing list by [email protected] a subscription request(an empty message with no subject is fine). While the GNU project includes Perl in its distributions, there's nosuch thing as "GNU Perl". Perl is not produced nor maintained by theFree Software Foundation. Perl's licensing terms are also more openthan GNU software's tend to be. You can get commercial support of Perl if you wish, although for mostusers the informal support will more than suffice. See the answer to"Where can I buy a commercial version of Perl?" for more information. Which version of Perl should I use?(contributed by brian d foy) There is often a matter of opinion and taste, and there isn't any oneanswer that fits everyone. In general, you want to use either the currentstable release, or the stable release immediately prior to that one.Currently, those are perl5.14.x and perl5.12.x, respectively. Beyond that, you have to consider several things and decide which is bestfor you. If things aren't broken, upgrading perl may break them (or at least issuenew warnings). The latest versions of perl have more bug fixes. The Perl community is geared toward supporting the most recent releases,so you'll have an easier time finding help for those. Versions prior to perl5.004 had serious security problems with bufferoverflows, and in some cases have CERT advisories (for instance,http://www.cert.org/advisories/CA-1997-17.html ). The latest versions are probably the least deployed and widely tested, soyou may want to wait a few months after their release and see whatproblems others have if you are risk averse. The immediate, previous releases (i.e. perl5.8.x ) are usually maintainedfor a while, although not at the same level as the current releases. No one is actively supporting Perl 4. Ten years ago it was a deadcamel carcass (according to this document). Now it's barely a skeletonas its whitewashed bones have fractured or eroded. The current leading implementation of Perl 6, Rakudo, released a "useful,usable, 'early adopter'" distribution of Perl 6 (called Rakudo Star) in July of2010. Please see http://rakudo.org/ for more information. There are really two tracks of perl development: a maintenance versionand an experimental version. The maintenance versions are stable, andhave an even number as the minor release (i.e. perl5.10.x, where 10 is theminor release). The experimental versions may include features thatdon't make it into the stable versions, and have an odd number as theminor release (i.e. perl5.9.x, where 9 is the minor release).
What are Perl 4, Perl 5, or Perl 6?In short, Perl 4 is the parent to both Perl 5 and Perl 6. Perl 5 is the oldersibling, and though they are different languages, someone who knows one willspot many similarities in the other. The number after Perl (i.e. the 5 after Perl 5) is the major releaseof the perl interpreter as well as the version of the language. Eachmajor version has significant differences that earlier versions cannotsupport. The current major release of Perl is Perl 5, first released in1994. It can run scripts from the previous major release, Perl 4(March 1991), but has significant differences. Perl 6 is a reinvention of Perl, it is a language in the same lineage butnot compatible. The two are complementary, not mutually exclusive. Perl 6 isnot meant to replace Perl 5, and vice versa. See What is Perl 6? belowto find out more. See perlhist for a history of Perl revisions. What is Perl 6?Perl 6 was originally described as the community's rewrite of Perl 5.Development started in 2002; syntax and design work continue to this day.As the language has evolved, it has become clear that it is a separatelanguage, incompatible with Perl 5 but in the same language family. Contrary to popular belief, Perl 6 and Perl 5 peacefully coexist with oneanother. Perl 6 has proven to be a fascinating source of ideas for thoseusing Perl 5 (the Moose object system is a well-known example). There isoverlap in the communities, and this overlap fosters the tradition of sharingand borrowing that have been instrumental to Perl's success. The currentleading implementation of Perl 6 is Rakudo, and you can learn more aboutit at http://rakudo.org. If you want to learn more about Perl 6, or have a desire to help inthe crusade to make Perl a better place then read the Perl 6 developerspage at http://www.perl6.org/ and get involved. "We're really serious about reinventing everything that needs reinventing."--Larry Wall How stable is Perl?Production releases, which incorporate bug fixes and new functionality,are widely tested before release. Since the 5.000 release, we haveaveraged about one production release per year. The Perl development team occasionally make changes to theinternal core of the language, but all possible efforts are made towardbackward compatibility. Is Perl difficult to learn?No, Perl is easy to start learning --and easy to keep learning. It lookslike most programming languages you're likely to have experiencewith, so if you've ever written a C program, an awk script, a shellscript, or even a BASIC program, you're already partway there. Most tasks only require a small subset of the Perl language. One ofthe guiding mottos for Perl development is "there's more than one wayto do it" (TMTOWTDI, sometimes pronounced "tim toady"). Perl'slearning curve is therefore shallow (easy to learn) and long (there'sa whole lot you can do if you really want). Finally, because Perl is frequently (but not always, and certainly not bydefinition) an interpreted language, you can write your programs and testthem without an intermediate compilation step, allowing you to experimentand test/debug quickly and easily. This ease of experimentation flattensthe learning curve even more. Things that make Perl easier to learn: Unix experience, almost any kindof programming experience, an understanding of regular expressions, andthe ability to understand other people's code. If there's something youneed to do, then it's probably already been done, and a working example isusually available for free. Don't forget Perl modules, either.They're discussed in Part 3 of this FAQ, along with CPAN, which isdiscussed in Part 2. How does Perl compare with other languages like Java, Python, REXX, Scheme, or Tcl?Perl can be used for almost any coding problem, even ones which requireintegrating specialist C code for extra speed. As with any tool it canbe used well or badly. Perl has many strengths, and a few weaknesses,precisely which areas are good and bad is often a personal choice. When choosing a language you should also be influenced by theresources, testing cultureand community which surrounds it. For comparisons to a specific language it is often best to createa small project in both languages and compare the results, make sureto use all the resources of each language,as a language is far more than just it's syntax. Can I do [task] in Perl?Perl is flexible and extensible enough for you to use on virtually anytask, from one-line file-processing tasks to large, elaborate 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 ofwhat they'd program in low-level languages like C or C++. It's ultimatelyup to you (and possibly your management) which tasks you'll use Perlfor and which you won't. If you have a library that provides an API, you can make any componentof it available as just another Perl function or variable using a Perlextension written in C or C++ and dynamically linked into your mainperl interpreter. You can also go the other direction, and write yourmain program in C or C++, and then link in some Perl code on the fly,to create a powerful application. See perlembed. That said, there will always be small, focused, special-purposelanguages dedicated to a specific problem domain that are simply moreconvenient for certain kinds of problems. Perl tries to be all thingsto all people, but nothing special to anyone. Examples of specializedlanguages that come to mind include prolog and matlab. When shouldn't I program in Perl?One good reason is when you already have an existingapplication written in another language that's all done (and donewell), or you have an application language specifically designed for acertain task (e.g. prolog, make). If you find that you need to speed up a specific part of a Perlapplication (not something you often need) you may want to use C,but you can access this from your Perl code with perlxs. What's the difference between "perl" and "Perl"?"Perl" is the name of the language. Only the "P" is capitalized.The name of the interpreter (the program which runs the Perl script)is "perl" with a lowercase "p". You may or may not choose to follow this usage. But never write "PERL",because perl is not an acronym. What is a JAPH?(contributed by brian d foy) JAPH stands for "Just another Perl hacker,", which Randal Schwartz usedto sign email and usenet messages starting in the late 1980s. Hepreviously used the phrase with many subjects ("Just another x hacker,"),so to distinguish his JAPH, he started to write them as Perl programs: - print "Just another Perl hacker,";
Other people picked up on this and started to write clever or obfuscatedprograms to produce the same output, spinning things quickly out ofcontrol while still providing hours of amusement for their creators andreaders. CPAN has several JAPH programs at http://www.cpan.org/misc/japh. How can I convince others to use Perl?(contributed by brian d foy) Appeal to their self interest! If Perl is new (and thus scary) to them,find something that Perl can do to solve one of their problems. Thatmight mean that Perl either saves them something (time, headaches, money)or gives them something (flexibility, power, testability). In general, the benefit of a language is closely related to the skill ofthe people using that language. If you or your team can be faster,better, and stronger through Perl, you'll deliver more value. Remember,people often respond better to what they get out of it. If you runinto resistance, figure out what those people get out of the otherchoice and how Perl might satisfy that requirement. You don't have to worry about finding or paying for Perl; it's freelyavailable and several popular operating systems come with Perl. Communitysupport in places such as Perlmonks ( http://www.perlmonks.com )and the various Perl mailing lists ( http://lists.perl.org ) means thatyou can usually get quick answers to your problems. Finally, keep in mind that Perl might not be the right tool for everyjob. You're a much better advocate if your claims are reasonable andgrounded in reality. Dogmatically advocating anything tends to makepeople discount your message. Be honest about possible disadvantagesto your choice of Perl since any choice has trade-offs. You might find these links useful: AUTHOR AND COPYRIGHTCopyright (c) 1997-2010 Tom Christiansen, Nathan Torkington, andother authors as noted. All rights reserved. This documentation is free; you can redistribute it and/or modify itunder the same terms as Perl itself. Irrespective of its distribution, all code examples here are in the publicdomain. You are permitted and encouraged to use this code and anyderivatives thereof in your own programs for fun or for profit as yousee fit. A simple comment in the code giving credit to the FAQ wouldbe courteous but is not required. | 
