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NAME
       perlfaq1 - General Questions About Perl

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

   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.

   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.  See perlhist
       (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 Free Software Foundation.  Perl's
       licensing terms are also more open than GNU software's



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       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.

   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 one answer that fits everyone. In general, you
       want to use either the current stable release, or the
       stable release immediately prior to that one.  Currently,
       those are perl5.10.x and perl5.8.x, respectively.

       Beyond that, you have to consider several things and
       decide which is best for you.

       o   If things aren't broken, upgrading perl may break them
           (or at least issue new warnings).

       o   The latest versions of perl have more bug fixes.

       o   The Perl community is geared toward supporting the
           most recent releases, so you'll have an easier time
           finding help for those.

       o   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 ).

       o   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.

       o   The immediate, previous releases (i.e. perl5.8.x ) are
           usually maintained for a while, although not at the
           same level as the current releases.

       o   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.

       o   There is no Perl 6 release scheduled, but it will be
           available when it's ready.  Stay tuned, but don't
           worry that you'll have to change major versions of
           Perl; no one is going to take Perl 5 away from you.

       o   There are really two tracks of perl development: a
           maintenance version and an experimental version.  The



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           maintenance versions are stable, and have an even
           number as the minor release (i.e. perl5.10.x, where 10
           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).

   What are Perl 4, Perl 5, or Perl 6?
       (contributed by brian d foy)

       In short, Perl 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, Perl 4 (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 perlhist for a history of Perl revisions.

   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.





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   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

   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 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).

   Is Perl difficult to learn?
       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 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, 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.



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       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 Perl modules, either.  They're discussed in Part 3
       of this FAQ, along with CPAN, which is discussed in Part
       2.

   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.

       Some comparison documents can be found at
       http://www.perl.com/doc/FMTEYEWTK/versus/ if you really
       can't stop yourself.

   Can I do [task] in Perl?
       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.
       See perlembed.

       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.

   When shouldn't I program in Perl?
       When your manager forbids it--but do consider replacing



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       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 multi-threaded shared-memory applications,
       or extremely large applications.  You'll notice that perl
       is not itself written in Perl.

       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. :-)

   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."

       Before the first edition of Programming perl, people
       commonly referred to the language as "perl", and its name
       appeared that way in the title because it referred to the
       interpreter. In the book, Randal Schwartz capitalised the
       language's name to make it stand out better when typeset.
       This convention was adopted by the community, and the
       second edition became Programming Perl, using the
       capitalized version of the name to refer to the language.

       You may or may not choose to follow this usage.  For
       example, parallelism means "awk and perl" and "Python and
       Perl" look good, 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.

   Is it a Perl program or a Perl script?
       Larry doesn't really care.  He says (half in jest) that "a
       script is what you give the actors.  A program is what you
       give the audience."

       Originally, a script was a canned sequence of normally
       interactive commands--that is, a chat script.  Something
       like a UUCP or PPP chat script or an expect script fits
       the bill nicely, as do configuration scripts run by a
       program at its start up, such .cshrc or .ircrc, for
       example.  Chat scripts were just drivers for existing



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       programs, not stand-alone programs in their own right.

       A computer scientist will correctly explain that all
       programs are interpreted and that the only question is at
       what level.  But if you ask this question of someone who
       isn't a computer scientist, they might tell you that a
       program has been compiled to physical machine code once
       and can then be run multiple times, whereas a script must
       be translated by a program each time it's used.

       Now that "script" and "scripting" are terms that have been
       seized by unscrupulous or unknowing marketeers for their
       own nefarious purposes, they have begun to take on strange
       and often pejorative meanings, like "non serious" or "not
       real programming".  Consequently, some Perl programmers
       prefer to avoid them altogether.

   What is a JAPH?
       (contributed by brian d foy)

       JAPH stands for "Just another Perl hacker,", which Randal
       Schwartz used to sign email and usenet messages starting
       in the late 1980s. He previously 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 obfuscated programs to produce the same output,
       spinning things quickly out of control while still
       providing hours of amusement for their creators and
       readers.

       CPAN has several JAPH programs at
       http://www.cpan.org/misc/japh .

   Where can I get a list of Larry Wall witticisms?
       (contributed by brian d foy)

       Google "larry wall quotes"! You might even try the "I feel
       lucky" button.  :)

       Wikiquote has the witticisms from Larry along with their
       source, including his usenet postings and source code
       comments.

       If you want a plain text file, try
       http://www.cpan.org/misc/lwall-quotes.txt.gz .

   How can I convince others to use Perl?
       (contributed by brian d foy)

       Appeal to their self interest! If Perl is new (and thus



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       scary) to them, find something that Perl can do to solve
       one of their problems. That might 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 of the people using that language. If you or
       your team can be more 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 run into
       resistance, figure out what those people get out of the
       other choice and how Perl might satisfy that requirement.

       You don't have to worry about finding or paying for Perl;
       it's freely available and several popular operating
       systems come with Perl. Community support in places such
       as Perlmonks ( http://www.perlmonks.com ) and the various
       Perl mailing lists ( http://lists.perl.org ) means that
       you can usually get quick answers to your problems.

       Finally, keep in mind that Perl might not be the right
       tool for every job. You're a much better advocate if your
       claims are reasonable and grounded in reality.
       Dogmatically advocating anything tends to make people
       discount your message. Be honest about possible
       disadvantages to your choice of Perl since any choice has
       trade-offs.

       You might find these links useful:

       o   http://perltraining.com.au/whyperl.html

       o   http://www.perl.org/advocacy/whyperl.html

REVISION
       Revision: $Revision: 1.11 $

       Date: $Date: 2009/10/12 18:24:47 $

       See perlfaq for source control details and availability.

AUTHOR AND COPYRIGHT
       Copyright (c) 1997-2009 Tom Christiansen, Nathan
       Torkington, and other authors as noted. All rights
       reserved.

       This documentation is free; you can redistribute it and/or
       modify it under the same terms as Perl itself.

       Irrespective of its distribution, all code examples here
       are in the public domain.  You are permitted and
       encouraged to use this code and any derivatives thereof in
       your own programs for fun or for profit as you see fit.  A
       simple comment in the code giving credit to the FAQ would



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       be courteous but is not required.
























































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