Subject: Perl FAQ part 1 of 0..9: General Questions [Periodic Posting]
From: PerlFAQ <[email-masked]>
Cc: [email-masked]
Date: 4 May 1997 21:47:06 GMT
Newsgroups: comp.lang.perl.misc,comp.lang.perl.announce

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

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.

    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.

  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.

  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.

  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).

  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.

  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.

  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.

  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. :-)

  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.

  Is it a Perl program or a Perl script?

    It doesn't matter.

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

  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 .

  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 .

  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 *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.

AUTHOR AND COPYRIGHT
    Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights
    reserved. See the perlfaq manpage for distribution information.

-- 
	Tom Christiansen	[email-masked]

    I won't mention any names, because I don't want to get sun4's into
    trouble...  :-)     --Larry Wall in <[email-masked]>