perlfaq1.pod

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=head1 NAME

perlfaq1 - General Questions About Perl ($Revision: 1.23 $, $Date: 1999/05/23 16:08:30 $)

=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
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.

=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
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 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
nntp://news.perl.com/perl.porters-gw/ and the Deja archive at
http://www.deja.com/ using the perl.porters-gw newsgroup, or you can
subscribe to the mailing list by sending [e-mail]
a subscription request.

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.

=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, long ago and
far away.  Sure, it's stable, but so is anything that's dead; in fact,
perl4 had been called a dead, flea-bitten camel carcass.  The most recent
production release is 5.6 (although 5.005_03 is still supported).
The most cutting-edge development release is 5.7.  Further references
to the Perl language in this document refer to the production release
unless otherwise specified.  There may be one or more official bug fixes
by the time you read this, and also perhaps some experimental versions
on the way to the next release.  All releases prior to 5.004 were subject
to buffer overruns, a grave security issue.

=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 ground-up rewrite of the original
perl source code from releases 1 through 4.  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. 
See L<perltrap/"Perl4 to Perl5 Traps">.

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.

See L<perlhist> for a history of Perl revisions.

=head2 What is perl6?

At The Second O'Reilly Open Source Software Convention, Larry Wall            
announced Perl6 development would begin in earnest. Perl6 was an oft
used term for Chip Salzenberg's project to rewrite Perl in C++ named
Topaz. However, Topaz should not be confused with the nisus to rewrite
Perl while keeping the lessons learned from other software, as well as
Perl5, in mind.

If you have a desire to help in the crusade to make Perl a better place
then peruse the Perl6 developers page at http://www.perl.org/perl6/ and 
get involved.

The first alpha release is expected by Summer 2001.

"We're really serious about reinventing everything that needs reinventing."
--Larry Wall

=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
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).

=head2 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.

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 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
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://language.perl.com/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 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.