IRIX Base Documentation 1998 November/IRIX 6.5.2 Base Documentation November 1998.img/usr/share/catman/u_man/cat1/perlfaq1.z/perlfaq1

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     perlfaq1 - General Questions About Perl ($Revision: 1.12 $, $Date:
     1997/04/24 22:43:34 $)

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     This section of the FAQ answers very general, high-level questions about
     Perl.

     WWWWhhhhaaaatttt iiiissss PPPPeeeerrrrllll????

     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.

     WWWWhhhhoooo ssssuuuuppppppppoooorrrrttttssss PPPPeeeerrrrllll????  WWWWhhhhoooo ddddeeeevvvveeeellllooooppppssss iiiitttt????  WWWWhhhhyyyy iiiissss iiiitttt ffffrrrreeeeeeee????

     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.

     WWWWhhhhiiiicccchhhh vvvveeeerrrrssssiiiioooonnnn ooooffff PPPPeeeerrrrllll sssshhhhoooouuuulllldddd IIII uuuusssseeee????






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PPPPEEEERRRRLLLLFFFFAAAAQQQQ1111((((1111))))                                                        PPPPEEEERRRRLLLLFFFFAAAAQQQQ1111((((1111))))



     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.

     WWWWhhhhaaaatttt aaaarrrreeee ppppeeeerrrrllll4444 aaaannnndddd ppppeeeerrrrllll5555????

     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.

     HHHHoooowwww ssssttttaaaabbbblllleeee iiiissss PPPPeeeerrrrllll????

     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).

     IIIIssss PPPPeeeerrrrllll ddddiiiiffffffffiiiiccccuuuulllltttt ttttoooo lllleeeeaaaarrrrnnnn????

     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



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     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.

     HHHHoooowwww ddddooooeeeessss PPPPeeeerrrrllll ccccoooommmmppppaaaarrrreeee wwwwiiiitttthhhh ooootttthhhheeeerrrr llllaaaannnngggguuuuaaaaggggeeeessss lllliiiikkkkeeee JJJJaaaavvvvaaaa,,,, PPPPyyyytttthhhhoooonnnn,,,, RRRREEEEXXXXXXXX,,,,
     SSSScccchhhheeeemmmmeeee,,,, oooorrrr TTTTccccllll????

     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.

     CCCCaaaannnn IIII ddddoooo [[[[ttttaaaasssskkkk]]]] iiiinnnn PPPPeeeerrrrllll????

     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.






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     WWWWhhhheeeennnn sssshhhhoooouuuullllddddnnnn''''tttt IIII pppprrrrooooggggrrrraaaammmm iiiinnnn PPPPeeeerrrrllll????

     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. :-)

     WWWWhhhhaaaatttt''''ssss tttthhhheeee ddddiiiiffffffffeeeerrrreeeennnncccceeee bbbbeeeettttwwwweeeeeeeennnn """"ppppeeeerrrrllll"""" aaaannnndddd """"PPPPeeeerrrrllll""""????

     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.

     IIIIssss iiiitttt aaaa PPPPeeeerrrrllll pppprrrrooooggggrrrraaaammmm oooorrrr aaaa PPPPeeeerrrrllll ssssccccrrrriiiipppptttt????

     It doesn't matter.

     In "standard terminology" a _p_r_o_g_r_a_m has been compiled to physical machine
     code once, and can then be be run multiple times, whereas a _s_c_r_i_p_t 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 byte code 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.

     WWWWhhhhaaaatttt iiiissss aaaa JJJJAAAAPPPPHHHH????

     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 .





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     WWWWhhhheeeerrrreeee ccccaaaannnn IIII ggggeeeetttt aaaa lllliiiisssstttt ooooffff LLLLaaaarrrrrrrryyyy WWWWaaaallllllll wwwwiiiittttttttiiiicccciiiissssmmmmssss????

     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 .

     HHHHoooowwww ccccaaaannnn IIII ccccoooonnnnvvvviiiinnnncccceeee mmmmyyyy ssssyyyyssssaaaaddddmmmmiiiinnnn////ssssuuuuppppeeeerrrrvvvviiiissssoooorrrr////eeeemmmmppppllllooooyyyyeeeeeeeessss ttttoooo uuuusssseeee vvvveeeerrrrssssiiiioooonnnn
     ((((5555////5555....000000004444////PPPPeeeerrrrllll iiiinnnnsssstttteeeeaaaadddd ooooffff ssssoooommmmeeee ooootttthhhheeeerrrr llllaaaannnngggguuuuaaaaggggeeee))))????

     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 _c_o_m_p_r_e_h_e_n_s_i_v_e
     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.

AAAAUUUUTTTTHHHHOOOORRRR AAAANNNNDDDD CCCCOOOOPPPPYYYYRRRRIIIIGGGGHHHHTTTT
     Copyright (c) 1997 Tom Christiansen and Nathan Torkington.  All rights
     reserved.  See the _p_e_r_l_f_a_q manpage for distribution information.











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