X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlfaq1.pod;h=d04fa28f1c085157e35e7515c1056edff825c8fd;hb=dbef3c66e2761d118774f973c961faa9b1e467d9;hp=a9a5fd4858625837a3416b97c745cdcbb94976ba;hpb=c90c0ff485be15aaf3ee20121299cb014ee6b1ff;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perlfaq1.pod b/pod/perlfaq1.pod index a9a5fd4..d04fa28 100644 --- a/pod/perlfaq1.pod +++ b/pod/perlfaq1.pod @@ -1,6 +1,6 @@ =head1 NAME -perlfaq1 - General Questions About Perl ($Revision: 1.12 $, $Date: 1997/04/24 22:43:34 $) +perlfaq1 - General Questions About Perl ($Revision: 9681 $) =head1 DESCRIPTION @@ -29,14 +29,21 @@ 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. +distribution for more details. See L (new as of 5.005) +for Perl's milestone releases. + +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 the archives at +http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/ +and http://archive.develooper.com/perl5-porters@perl.org/ +or the news gateway nntp://nntp.perl.org/perl.perl5.porters or +its web interface at http://nntp.perl.org/group/perl.perl5.porters , +or read the faq at http://dev.perl.org/perl5/docs/p5p-faq.html , +or you can subscribe to the mailing list by sending +perl5-porters-request@perl.org a subscription request +(an empty message with no subject is fine). 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 @@ -49,33 +56,133 @@ users the informal support will more than suffice. See the answer to =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 Version 4 is old, limited, and -no longer maintained; its last patch (4.036) was in 1992.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 most -recent production release is 5.004. Further references to the Perl -language in this document refer to this production release unless -otherwise specified. There may be one or more official bug fixes for -5.004 by the time you read this, and also perhaps some experimental -versions on the way to the next release. - -=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. +(contributed by brian d foy) + +There is often a matter of opinion and taste, and there isn't any one +answer that fits anyone. In general, you want to use either the current +stable release, or the stable release immediately prior to that one. +Currently, those are perl5.8.x and perl5.6.x, respectively. + +Beyond that, you have to consider several things and decide which is best +for you. + +=over 4 + +=item * + +If things aren't broken, upgrading perl may break them (or at least issue +new warnings). + +=item * + +The latest versions of perl have more bug fixes. + +=item * + +The Perl community is geared toward supporting the most recent releases, +so you'll have an easier time finding help for those. + +=item * + +Versions prior to perl5.004 had serious security problems with buffer +overflows, and in some cases have CERT advisories (for instance, +http://www.cert.org/advisories/CA-1997-17.html ). + +=item * + +The latest versions are probably the least deployed and widely tested, so +you may want to wait a few months after their release and see what +problems others have if you are risk averse. + +=item * + +The immediate, previous releases (i.e. perl5.6.x ) are usually maintained +for a while, although not at the same level as the current releases. + +=item * + +No one is actively supporting Perl 4. Five years ago it was a dead +camel carcass (according to this document). Now it's barely a skeleton +as its whitewashed bones have fractured or eroded. + +=item * + +There is no Perl 6 for the next couple of years. Stay tuned, but don't +worry that you'll have to change major versions of Perl soon (i.e. before +2008). + +=item * + +There are really two tracks of perl development: a maintenance version +and an experimental version. The maintenance versions are stable, and +have an even number as the minor release (i.e. perl5.8.x, where 8 is the +minor release). The experimental versions may include features that +don't make it into the stable versions, and have an odd number as the +minor release (i.e. perl5.9.x, where 9 is the minor release). + +=back + + +=head2 What are Perl 4, Perl 5, or Perl 6? + +(contributed by brian d foy) + +In short, Pelr 4 is the past, Perl 5 is the present, and Perl 6 is the +future. + +The number after perl (i.e. the 5 after Perl 5) is the major release +of the perl interpreter as well as the version of the language. Each +major version has significant differences that earlier versions cannot +support. + +The current major release of Perl is Perl 5, and was released in 1994. +It can run scripts from the previous major release, perl4 (March 1991), +but has significant differences. It introduced the concept of references, +complex data structures, and modules. The Perl 5 interpreter was a +complete re-write of the previous perl sources. + +Perl 6 is the next major version of Perl, but it's still in development +in both its syntax and design. The work started in 2002 and is still +ongoing. Many of the most interesting features have shown up in the +latest versions of Perl 5, and some Perl 5 modules allow you to use some +Perl 6 syntax in your programs. You can learn more about Perl 6 at +http://dev.perl.org/perl6/ . + +See L for a history of Perl revisions. + +=head2 What was Ponie? + +(contributed by brian d foy) + +Ponie stands for "Perl On the New Internal Engine", started by Arthur +Bergman from Fotango in 2003, and subsequently run as a project of The +Perl Foundation. It was abandoned in 2006 +(http://www.nntp.perl.org/group/perl.ponie.dev/487). + +Instead of using the current Perl internals, Ponie aimed to create a +new one that would provide a translation path from Perl 5 to Perl 6 +(or anything else that targets Parrot, actually). You would have been +able to just keep using Perl 5 with Parrot, the virtual machine which +will compile and run Perl 6 bytecode. + +=head2 What is Perl 6? + +At The Second O'Reilly Open Source Software Convention, Larry Wall +announced Perl 6 development would begin in earnest. Perl 6 was an oft +used term for Chip Salzenberg's project to rewrite Perl in C++ named +Topaz. However, Topaz provided valuable insights to the next version +of Perl and its implementation, but was ultimately abandoned. + +If you want to learn more about Perl 6, or have a desire to help in +the crusade to make Perl a better place then peruse the Perl 6 developers +page at http://dev.perl.org/perl6/ and get involved. + +Perl 6 is not scheduled for release yet, and Perl 5 will still be supported +for quite awhile after its release. Do not wait for Perl 6 to do whatever +you need to do. + +"We're really serious about reinventing everything that needs reinventing." +--Larry Wall =head2 How stable is Perl? @@ -85,17 +192,17 @@ 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 +backward compatibility. While not quite all Perl 4 scripts run flawlessly +under Perl 5, 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. +No, Perl is easy to start learning--and easy to keep learning. It looks +like most programming languages you're likely to have experience +with, so if you've ever written a C program, an awk script, a shell +script, or even a BASIC program, you're already partway 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 @@ -103,18 +210,18 @@ 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. +Finally, because Perl is frequently (but not always, and certainly not by +definition) an interpreted language, 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 +usually available for free. Don't forget Perl modules, either. +They're discussed in Part 3 of this FAQ, along with CPAN, which is discussed in Part 2. =head2 How does Perl compare with other languages like Java, Python, REXX, Scheme, or Tcl? @@ -127,22 +234,25 @@ 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. +Some comparison documents can be found at http://www.perl.com/doc/FMTEYEWTK/versus/ +if you really can't stop yourself. + =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. +Perl is flexible and extensible enough for you to use on virtually any +task, 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 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. +to create a powerful application. See L. That said, there will always be small, focused, special-purpose languages dedicated to a specific problem domain that are simply more @@ -152,7 +262,7 @@ 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 :-). +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 @@ -161,17 +271,14 @@ 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 +device drivers or context-switching code, complex multi-threaded 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. :-) +Perl remains fundamentally a dynamically typed language, not +a statically typed one. You certainly won't be chastised 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"? @@ -180,70 +287,125 @@ 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. +OK, while "awk and Perl" and "Python and perl" do not. But never +write "PERL", because perl is not an acronym, apocryphal +folklore and post-facto expansions notwithstanding. =head2 Is it a Perl program or a Perl script? -It doesn't matter. - -In "standard terminology" a I has been compiled to physical -machine code once, and can then be be run multiple times, whereas a -I