=head1 NAME
-perlfaq1 - General Questions About Perl ($Revision: 8539 $)
+perlfaq1 - General Questions About Perl
-=head1 DESCRIPTION
+=head1 DESCRIPTION
This section of the FAQ answers very general, high-level questions
about Perl.
=head2 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
+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
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.
+and even managers also use Perl. Maybe you should, too.
-=head2 Who supports Perl? Who develops it? Why is it free?
+=head2 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
+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
+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 L<perlhist> (new as of 5.005)
+distribution for more details. See L<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
+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
+perl5-porters-subscribe@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
+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
+users the informal support will more than suffice. See the answer to
"Where can I buy a commercial version of perl?" for more information.
=head2 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 anyone. In general, you want to use either the current
+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 perl5.8.x and perl5.6.x, respectively.
+Currently, those are perl5.14.x and perl5.12.x, respectively.
Beyond that, you have to consider several things and decide which is best
for you.
=item *
-The immediate, previous releases (i.e. perl5.6.x ) are usually maintained
+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.
=item *
-No one is actively supporting perl4.x. Five years ago it was a dead
-camel carcass (according to this document). Now it's barely a skeleton
+No one is actively supporting Perl 4. Ten 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 perl6.x 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).
+There is no Perl 6 release scheduled, but it will be available when
+it's ready. The joke is that it's scheduled for Christmas, but that we
+just don't know which one. 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.
=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
+and an experimental version. The 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).
=back
-=head2 What are perl4, perl5, or perl6?
+=head2 What are Perl 4, Perl 5, or Perl 6?
(contributed by brian d foy)
-In short, perl4 is the past, perl5 is the present, and perl6 is the
+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 perl5) is the major release
-of the perl interpreter as well as the version of the language. Each
+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 perl5, 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 perl5 interpreter was a
-complete re-write of the previous perl sources.
+The current major release of Perl is Perl 5, and was first 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.
-Perl6 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 perl5, and some perl5 modules allow you to use some
-perl6 syntax in your programs. You can learn more about perl6 at
-http://dev.perl.org/perl6/ .
+Perl 6 is the next major version of Perl, although it's not intended to
+replace Perl 5. It's still in development in both its syntax and
+design. The work started in 2002 and is still ongoing. Some 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. The current leading implementation of Perl 6 is Rakudo (
+http://rakudo.org ).
See L<perlhist> 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 perl6?
+=head2 What is Perl 6?
At The Second O'Reilly Open Source Software Convention, Larry Wall
-announced Perl6 development would begin in earnest. Perl6 was an oft
+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 Perl6, or have a desire to help in
-the crusade to make Perl a better place then peruse the Perl6 developers
+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 read the Perl 6 developers
page at http://dev.perl.org/perl6/ and get involved.
-Perl6 is not scheduled for release yet, and Perl5 will still be supported
-for quite awhile after its release. Do not wait for Perl6 to do whatever
+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."
=head2 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
+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
+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?
-No, Perl is easy to start learning--and easy to keep learning. It looks
+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
+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
+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
+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
+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.
+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?
-Favorably in some areas, unfavorably in others. Precisely which areas
+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
+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/
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
+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
+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 L<perlembed>.
+to create a powerful application. See L<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
+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.
=head2 When shouldn't I program in Perl?
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
+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
+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"?
-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. But never
-write "PERL", because perl is not an acronym, apocryphal
-folklore and post-facto expansions notwithstanding.
+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 I<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 I<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.
=head2 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."
+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
+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 F<.cshrc> or F<.ircrc>,
-for example. Chat scripts were just drivers for existing programs,
+for example. Chat scripts were just drivers for existing 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
+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 I<program> has been compiled to physical machine code
once and can then be run multiple times, whereas a I<script> must be
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
+like "non serious" or "not real programming". Consequently, some Perl
programmers prefer to avoid them altogether.
=head2 What is a JAPH?
print "Just another Perl hacker,";
-Note the trailing comma and space, which allows the addition of other
-JAxH clauses for his many other interests.
-
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
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,
+the 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 run
into resistance, figure out what those people get out of the other
=back
-=head1 REVISION
-
-Revision: $Revision: 8539 $
-
-Date: $Date: 2007-01-11 00:07:14 +0100 (Thu, 11 Jan 2007) $
-
-See L<perlfaq> for source control details and availability.
-
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997-2007 Tom Christiansen, Nathan Torkington, and
+Copyright (c) 1997-2010 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
+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
+see fit. A simple comment in the code giving credit to the FAQ would
be courteous but is not required.
https://perl5.git.perl.org / perl5.git / blobdiff