What is Perl? Programming language Perl detailed introduction to _perl

Perl's original designer was Larry Wall (Larry Wall), which was published on December 18, 1987. Perl borrows the features of C, sed, awk, shell scripting, and many other programming languages. Larry Wall Published version 1.0 of the Perl scripting language in newsgroup comp.sources.misc, when he was a programmer at Unisys company. Perl borrowed from the features of scripting languages such as SH, awk, and SED, trying to become a general-purpose UNIX scripting language that simplifies reporting processing.

Perl 2 was released in 1988, adding more features and having a better regular expression engine. Perl 3 and Perl 4 were released in 1989 and 1991 respectively, while Perl 5, released in 1994, is the most important version and is still under development. Perl 6, which was launched in 2000, completely rewrites Perl, and based on different principles, developers decided to make language specifications first. The release date of Perl 6 is considered Christmas, but it does not specify which year of Christmas.  Perl 5 released 16 editions, Perl 5.6 was released in 2000, and Perl 5.8 continued to develop throughout 2002-08, 5.10 in 2007, 5.12 in 2010, and thereafter Perl began releasing a monthly version of a stable release cycle, 5.14 was released in 2011, and 5.16 was released in 2012.

Perl is commonly referred to as the "utility Report Extraction Language" (Practicalextraction andreportlanguage), although sometimes referred to as the "sick Compromise Junk list" (pathologicallyeclectic rubbish Lister). It's the term, not just shorthand, Perl's creator, Larrywall first, but soon expands to the second. That's why "Perl" doesn't capitalize all the letters. There is no need to argue about that one right, Larry two all agree. You may also see "Perl," where all the letters are lowercase. Generally, "Perl", with uppercase P, refers to the language itself, while "Perl", lowercase p, refers to the interpreter that the program runs. The official website of Perl is www.perl.org.

Features of Perl
Perl's interpreter is open source freeware, and Perl doesn't have to worry about costs, Perl can run on most operating systems and can easily migrate to different operating systems.

Perl is a language that can accomplish tasks. From the outset, Perl was designed to simplify simple work without losing the ability to deal with difficult problems. It makes it easy to manipulate the languages of numbers, text, files and directories, computers and networks, especially programs. This language should be easy to run external programs and scan the output of these programs to get something interesting, and it should be easy to give these things you are interested in to other programs to do special processing, of course, this language should also be easily on any modern operating system can be ported to compile and run.

Perl Basic Syntax
scalar definition, beginning with $ number, such as: $num = 1;

Array definition, beginning with @, such as: @array = (1,2,3);

The array element is called @array [index], where index represents the array subscript, as in the previous example, the value of @array [0] is 1

Hash definition, beginning with%, such as:%hash= ("A", 1, "B", 2);

Hash call%hash, where key represents the key value, as in the previous example, the value of%hash{"B"} is 1

The philosophy of Perl
Perl pursues simplicity, solves a general problem and completes it with a few lines of code. A slightly more complex problem code will not exceed a screen! In fact, most of the programs that most people write in Perl are not more than 100 lines.

Perl was originally designed as a Unix glue language, but she was already ported to most other operating systems. Because Perl can run almost anywhere, Perl can be said to be the most portable programming environment today. To write a portable C + + program, you have to add a whole bunch of #ifdef tags to the program to differentiate between the different systems. To write portable Java programs, you must understand the nature of each new Java implementation. To write a portable shell, you might want to remember the syntax of each command on each operating system, and you might be able to find something public when you're lucky. To write a portable Visual Basic program, you just need to have a more flexible definition of "porting."

We are pleased that Perl avoids all these problems, while preserving many of the advantages of these languages while still having some of its own characteristics. The features of Perl come from many aspects: the tools of its feature set, the creativity of the Perl community, and the great environment of open source movement. However, many of these features are mixed; Perl has a complex life, and it always sees things as a different aspect of merit, not a weakness. Perl is the "take the blame for me" language. If you feel like you're stuck in a mess and want to be free, then use Perl.

Perl is trans-cultural. The explosive growth of Perl is largely due to the desire of former Unix system programmers, who want to take as many things from their "home" as possible. For them, Perl is a portable Unix culture distiller, an oasis in the "blocked" desert. From another point of view, Perl can work in another direction: Web designers working on Windows are often happy to find that their Perl programs can run on Unix servers without modification.

Although Perl is very popular among system programmers and web designers, it is only because they were the first to discover Perl, and Perl can be used for a wider range of purposes. Starting with Perl's earliest text-processing language, it has developed into a very complex, universal programming language, as well as a complete development environment, including debuggers, regulators, cross-references, compilers, libraries, syntax prompt editors, and all the hooks that all other "real" programming languages have, as long as you need them. Of course these are things that make it possible for us to deal with difficult problems, and many other languages can do that. Perl is Perl because it never loses other features because it keeps simplicity simple.

Because Perl is powerful and useful, it is widely used in every aspect of daily life, from aerospace engineering to molecular biology, from mathematics to linguistics, from graphic processing to document processing, from database operations to network management. Many people use Perl to quickly process large amounts of data that are difficult to analyze or convert, whether you're dealing with DNA sequences, web pages, or the future of belly-pig skin. In fact, there is a joke in the Perl community that the next time the stock market crash is likely to be a bug in a script written by a guy. (However, in a happy sense, any stock analyst who is still unemployed is still available.) )

There are many reasons for the success of Perl. Perl was a successful open source project long before the name of the Open-source software appeared. Perl is free, and will always be free to go on. You can use Perl on any suitable occasion, just follow a very free copyright. If you're doing business and you want to use Perl, then use it. You can embed Perl in the business software you write without paying any fees or restrictions. If you run into a problem that a Perl community can't solve, you also have the last resort: the source program itself. The Perl community will not rent your business secrets under the guise of "Upgrades", and the Perl community will not "shut out" or leave you alone.

Perl is free software and this is certainly helpful. But this is not enough to explain the Perl phenomenon, because many free packages are not thriving. Perl is not only free, but also fun. People think they can be creative in Perl, because they have freedom of expression: they can choose whether to optimize for the speed of the computer or for the programmer's speed, whether it is verbose or concise, whether to choose readability or maintainability, or to choose reusability, portability, acceptability and imparting, and so on. If you go into a vague Perl game, you can even optimize for ambiguity.

Perl can give you all that freedom because it's a split-personality language, and Perl is a very simple and rich language. Perl takes good ideas from elsewhere and installs them into an easy-to-use framework. For people who just like her, Perl is a practical extraction and reporting language (practical extractoin and report Language). For those who love her, she is a twisted electronic waste maker (pathologically electric rubbish Lister). Perl is a meaningless repetition in the eyes of a few, but the world needs a little redundancy, and the leaner always want to separate things, and we always try to merge them together.

There are a number of reasons why Perl is a simple language. For example, you can compile a Perl program without having to know any specific instructions-just do it as a batch or shell script. The type and structure of Perl are easy to use and understand. Perl has no limits on your data-how long your strings and arrays can take (as long as you have enough memory), and they all grow automatically. Perl does not force you to learn new syntax and semantics, and Perl borrows grammar from many other languages you already know (such as C, awk, BASIC and Python, English, Greek, etc.). In fact, any programmer can read its meaning from a well written Perl code snippet.

The most important thing is that you can start writing useful programs without first learning everything from Perl. You can write a small Perl program. You can also write Perl programs like kids, and we promise not to laugh at you. Or, to be more precise, we never joke about the creativity of children doing things. Many of the ideas in Perl are borrowed from natural languages, and one of the best ideas is that you can use a subset of these languages as long as you can articulate your own meaning. Perl culture can accept members of any degree of proficiency. We're not going to put a language cop behind your back. If your boss doesn't fire you and your Perl script can do the job, it's "right."

Although Perl is simple, it is still a very rich language, and if you want to use those features, you need to learn something, which is also a tuition fee that turns the puzzle into a simple one. While it will take some time for you to absorb all the things Perl can do, you'll be happy to see that Perl can do this when you need them.

As a result of Perl's inheritance, even though it is also a rich feature when used as a data-inductive language, Perl was initially designed to be able to browse files, scan large amounts of text and generate dynamic data and print out well-formed reports of that data. However, Perl began to become popular, so it became a language that could manipulate file systems, process management, database management, C/s programming and security programming, web information management, and even object-oriented and functional programming. And these features are not just in Perl, each new feature communicates well with other things, and don't forget that Perl was designed to be a glue language from the start.

And Perl does not just glue its own features. Perl is designed to be a language that can be extended with modules. You can quickly design, write, debug, and deploy Perl applications in Perl, and you can easily extend these applications as needed. You can embed Perl in other languages, and you can embed other languages in Perl. With the module input mechanism, you can use these external extensions as intrinsic to Perl. Those object-oriented external libraries still maintain object-oriented features within Perl.

Perl also assists you in many other ways. Unlike a strict command file and a shell script that executes one command at a time, Perl first compiles your program quickly into an internal format. As with any other compiler, this is a time to make a variety of optimizations and give you feedback on any problems you encounter. Once Perl's compiler front-end is satisfied with your program, it gives the intermediate code to the interpreter (or to other modules that generate C or bytecode). It sounds complicated, but Perl's compilers and interpreters are quite efficient at doing this, and our compilation-run-modify process is almost always in seconds. Coupled with many other development features of Perl, this fast-changing role model is ideal for quick prototyping. Then, as your program matures, you can gradually tighten the nuts on your body and reduce the loose reinforcement notation. If you do well, Perl can do the same for you.

Perl can also help you write more secure programs. In addition to the typical security interfaces provided by other languages, Perl provides you with a mechanism for tracking data to protect you against accidental security errors that can be prevented before a disaster occurs. Finally, Perl allows you to set up a special protective compartment to run the Perl code that is not in the source, to prevent dangerous operations.

But, to be paranoid, most of what Perl does for you has nothing to do with Perl itself, but with people who use Perl. Frankly, people in the Perl community can be said to be the most enthusiastic people on Earth. If the Perl movement had a little bit of religious overtones, then that's the heart of it. Larry wants the Perl community to run like a small piece of heaven, and now it seems that his wishes are basically fulfilled. We also ask you to make your own efforts to that end.

Perl is strong because there are CPAN, CPAN, there are countless open source modules, from scientific computing to desktop applications to the network and so on all aspects have a large number of modules! And now there are countless people in the world to add modules to the above! If you want to use Perl to achieve a certain function, do not do it yourself, search on the cpan above, most will get the results! CPAN ("The Comprehensive Perl Archive Network" Comprehensive Perl Archive Network) is the central repository for anything that is related to Perl. It contains the wisdom gathered from the entire Perl community: Hundreds of Perl modules and scripts, the equivalent of several books, and the entire Perl release. If something is written in Perl, and this thing is useful and free, it is likely to be on the CPAN. CPAN has a mirror image all over the world, and you can find the mirror that is closest to you on the CPAN road sign in Http://www.perl.com/CPAN. The sign will remember which mirror you chose, and you will automatically redirect to the mirror when you visit http://www.perl.com/CPAN/(note the last slash) later. Alternatively, you can start with www.cpan.org. The interface of this station is different, but the data is the same.

Perl culture
1. The Times Create Heroes
To understand why Perl is defined in the way that it is (or why it is not defined as otherwise), we must first understand why Perl is. So, let's dig up a history book of Dust and Ashes first ....

Back to 1986, Larry is a system programmer in the development of a multi-tiered, secure WAN project. He was in charge of such a system, the system is made up of three VAX on the West Coast and a system connected to a similar configuration on the East coast via an encrypted 1200 baud serial line, and Larry's main job is to support (he is not a programmer for the project, just a system expert), So he had the opportunity to use his three strengths (laziness, impatience, and arrogance) to develop and improve all the useful tools--RN, Patch, and warp. (Note: It was at this time that Larry was drawn into the category of "Computer Animals", which was judged on the basis of the irresistible desire of those people to "add a trait", as this behavior was almost a biological necessity. After all, if life is too complicated, isn't the program? Especially in the case of RN, it should be treated as an advanced AI project because they can read the news for you. Of course, some people are already saying that the patch program is too complicated. )

One day, Larry just tore the RN into pieces and put it in his catalogue, and the big manager ran in and said, "Larry, we need a management configuration that controls all six VAX and six suns." We want it in one months, you make one! ”

So, Larry, who never escapes from work, starts asking himself what is the best way to do a two-coast CM system, it must not start from scratch, and can also look up two of coastal problem reports as well as approvals and controls. The answer he came up with was only one word: b-news. (Note: The second implementation of Usenet transmission software.) )

Larry started installing news software on these machines and added two control commands: a "append" command to append content to an existing article, and a "synchronize" command to maintain the same number of articles on two coasts. CM can be done with RCS (version control system), while approval and control can be done in news and RN. It's a good time.

Then the big administrator lets him generate the report. The news is maintained in a separate file in the core machine, and there are many cross-references between the files. Larry's first reaction was "in awk." "Unfortunately, at that time, Awk was unable to open and close multiple files based on the information in the file." Larry didn't want to write a special purpose tool, and the result was a new language. Originally this new language was not called Perl. Larry and his colleagues and relatives (Dan Faigin, who wrote this history, and Mark Biggar, his brother-in-law, helped in the initial design phase) exchanged a lot of names. Larry actually considers and discards all the three or four-letter words in the dictionary. The first name was "Gloria", named after his baby (and his wife), but he soon found that there was too much family chaos.

Then the name became "Pearl", and in the end it became our current "Perl", in part because Larry saw another introduction to the language called Pearl, but the main reason was that he was too lazy to always knock five keys. Of course, Perl can be used as a four-letter word. (However, you will notice that there are remnants of the previous initials: "Practical extraction and Language".) )

The earliest Perl did not have as many features as today's Perl. There were pattern matching and file handles, scalar, formatted, but few functions, no related arrays, and only a regular expression (borrowed from Rn) that was not implemented very well. The man page also has only 15 pages. But Perl is faster than SED and awk, and begins to be used in other applications of the project.

But other places are starting to need Larry again. One day another big manager came and said, "Larry, give r&d support." "and Larry said," Okay. He brought Perl and soon discovered that it was becoming a good tool for system management. He borrowed Henry Spencer's beautiful regular expression package and made it more manly (though Henry might not want to consider these features during dinner). Then Larry adds most of the features he wants, and some of the features that others want. It then publishes Perl to the Web. (Note: Even more surprising, he worked in the Jet Propulsion Laboratory (JPL), followed by Netlabs and Seagate, and continued to publish new Perl. Now, others do most of the work, while Larry pretends to be O ' Reilly & Associates (a small company that prints brochures about computers and related things.) The rest is history. (Note: And these things are an annotation of history.) When it started Perl, Larry had broken the RN into pieces and was ready for a full rewrite. But as he started working in Perl, Larry didn't touch the RN again, and it was still fragmented. Sometimes Larry says he'll rewrite the RN in Perl, but never take it seriously. )

And that's what happened: Perl 1.0 was released on December 18, 1987; Some people are still serious about Perl's birthday. Perl 2.0 was released in June 1988, and Randal Schwartz began the legend of the signature of "another Perl hacker". In 1989, Tom Christiansen the first public Perl tutorial in Baltimore Usenix. This language was first published and distributed under the GNU Public Copyright (GPL) in October 1989, when Perl 3.0 began.

Larry wrote the first Perl poem in March 1990 (see the next section). Then he and Randal wrote the first edition of the book, the Pink Camel, which was released in the early 1991. Perl 4.0 was then released immediately, including the artistic License (art copyright), in addition to the GPL.

The long-awaited Perl 5 was released in October 1994. This is a fully rewritten version of Perl, which includes objects and modules. The advent of Perl 5 has even been mentioned in the Ecomomist magazine. By the year 1995, CPAN was formally introduced to the Perl community. In 1996, Jon Orwant began publishing the Perl Journal magazine. After a long period of speculation, the second edition of the book, the Blue Camel, was published at the end of that year. The first O ' Reilly Perl Conference (TPC) was held in San Jose, California, in the summer of 1997. Now, significant time is occurring almost every day, so for the rest of history, check the Perl annals on Cpast (Comprehensive Perl Arcana Society Tapestry).

2. Perl poetry
The imitation of the poetry in the assistant box was posted on April Fool's Day in 1990 on Usenet. We put it here without comment, just to show how disgusting the metaphor of a typical programming language really is. This is probably true of all things that have literary value. Larry was feeling a lot easier after "Black Perl", originally written for Perl 3, after the inability to parse through Perl 5.

However, Larry's own anthology was fortunate to be overshadowed by the Sharon Hopkins, the Queen of Perl poetry. She wrote quite a few Perl poems, as well as some of her articles on Perl poetry, which she took out at the 1992 Usenet Winter Technical Convention, titled "Camels and Needles:computer poetry meets the Perl progr Amming Language ". (This article can be found in the misc/poetry.ps of CAPN.) Besides being the most prolific Perl poet, Sharon is the author of the following poem, one of the most widely published, and once published in Economist and Guardian magazine:

Copy Code code as follows:

#!/usr/bin/perl
Appeal:
Listen (please, please);
Open yourself, wide;
Join (you, ME),
Connect (Us,together),
Tell me.
Do something if distressed;
@dawn, dance;
@evening, sing;
Read (books, $poems, stories) until peaceful;
Study if able;
Write me if-you-please;
Sort your feelings, reset goals, seek (friends, family, anyone);
Do*not*die (like this)
If sin abounds;
Keys (hidden), open (locks, doors), tell secrets;
Don't, i-beg-you, close them, yet.
Accept (yourself, changes),
Bind (grief, despair);
Require truth, goodness if-you-will, each moment;
Select (always), Length (of-days)
# Listen (a Perl poem)
# Sharon Hopkins
# rev June 19, 1995
Perl poetry
Article 970 of Comp.lang.perl:
Path:jpl-devvax!pl-dexxav!lwall
From:lwall@jpl-dexxav. JPL. NASA.gov (Larry Wall)
Newsgroups:news.groups,rec.arts.poems,comp.lang.perl
Subject:call for DISCUSSION:comp.lang.perl.poems
Message-id:
Date:1 APR 00:00:00 GMT
Reply-to:lwall@jpl-devvax. JPL. Nsas.gov (Larry Wall)
Organization:jet prepulsion Laboratory, Pasadena, CA
lines:61

It has come to I attention that there are a crying need for a where people to express both their emotional and technic Al Natures simultaneously. Several people have sent me some items which don ' t fit to any
Newsgroup. Perhaps it ' s because I recently posted to both Comp.lang.perl and to Rec.arts.poems, but people-seem to be writing poems I n Perl, and they ' re asking me where they should post them. Here is a sampling:
From a graduate student (in finals week), the following haiku:

Study, write, study,
Do review (all word) if time.
Close book. Sleep? What ' s that?
And someone writing from Fort Lauderdale writes:
Sleep, close together,
Sort of sin each spring & wait;
50% die
A person who wishes to remain anonymous wrote the following example of ' Black Perl '. (The Pearl poet would have been shocked, no doubt.)

Beforehand:close door, each window & exit; Wait for until time.
Open Spellbook, study, read (scan, select, tell us);
Write it, print the hex while each watches,
Reverse its length, write again;
Kill spiders, pop them, chop, split, kill them.
Unlink arms, SHIFT, wait & Listen (listening, wait),
Sort the flock (then, warn the "goats" & Kill the "sheep");
Kill them, dump qualms, shift moralities,
Values aside, each one;
Die sheep! Die to reverse the system
You accept (reject, respect);
Next step,
Kill the next sacrifice, each sacrifice,
Wait, redo ritual until "all the spirits are pleased";
Do it ("as they say").
Do It (*everyone***must***participate***in***forbidden**s*e*x*).
return to last victim; Package body;
Exit crypt (Time, Times & ' half a Time ') & Close it,
Select (quickly) & warn your next victim;
Afterwords:tell nobody.
Wait for until time;
Wait until next year, next decade;
Sleep, sleep, die yourself,
Die at last

I tried that, and it actually parses in Perl.  It doesn ' t appear to do anything useful, however. I am I am glad, actually ... I hereby propose the creation of Comp.lang.perl.poems as a place for such items, so we don ' t clutter the perl or poems new  Sgroups with things this may is of interest to neither. Or, alternately, we should create rec.arts.poems.perl for items such as those above which merely parse, and don ' t do Anyth  ing useful.  (There is precedent in Rec.arts.poems and after all.) Then also create comp.lang.perl.poems for poems that actually does something, such as this haiku to my own:

Print STDOUT Q
Just another Perl hacker,
Unless $spring

Larry Wall lwall@jpl-devvax.jpl.nasa.gov

The old Perl never stops the pace of innovation, July 18, Perl 5.8.0 released.
The highlights of 5.8.0 include:
-Better Unicode support:
Since version 5.6, UNICODE support has been dramatically updated at various levels:
-Support for Unicode 3.2.0 Edition (Perl 5.6.1 Support 3.0.1 Edition)
-Provide a more general and smooth Unicode environment at the language and internal levels
-Regular expressions can match Unicode
-Provide Encode modules to support existing coding methods (including various medium/Japanese/Korean systems)

-Multithreading Execution Mode:
"Interpreter multithreading" (Interpreter threads, abbreviated "ithreads") is a new multithreaded execution pattern. We strongly recommend that you use it instead of the older version of the "5.005-threading Method" mode. The main difference between the two is that the ithreads must clearly declare the information to be shared.

-New input/output mode:
The new Perlio model also provides a cross-platform stdio implementation of the source hierarchy, as well as a richer output control architecture.

-More precise values:
The previous version of Perl relied on the string/numeric conversion functions on your system; This often results in a cross-platform barrier, as well as erroneous calculations.

-64-bit support:
The current 64-bit support is mature-if your system supports a 64-bit integer or address space, you can specify these features at compile time.

-Secure signal (signal) Processing:
In previous versions, Perl might have broken the internal state of the interpreter when it received the signal.

-A large number of new modules:
DIGEST::MD5, File::temp, Filter::simple, Libnet, List::util,memoize, Mime::base64, Scalar::util, Storable, Switch,Test :: More, Test::simple, text::balanced, Tie::file, ...

-Thorough compatibility testing:
Perl now has six times times the 5.6 version of the test suite, and daily installation test on a variety of platforms.

Compatibility
-Binary files are incompatible:
Due primarily to perlio imports, there is no "binary compatibility" between Perl 5.8 and previous versions of Perl. You may need to compile each XS extension module again.

-AIX Dynamic loading:
In order to be more compatible with other programs on the AIX system, Perl enabled dynamic loading of the system on the AIX system, rather than the previous simulation.

-Deactivate the Perl Malloc memory configuration on the 64-bit platform:
Perl's malloc function seems to have many problems with 64 more than a specific address machine. Therefore, we now preset to use the system native malloc function.

-The hash order changes again:
The hash function inside Perl is changed to a better version, but as long as your source code does not rely on a specific hash key sequence, this is no problem.

-My properties are handled in the execution phase:
The properties of my () variable are currently being processed in the execution phase, not the compile phase.

-REF (...) replaces SCALAR (...):
To conform to the result of ref (), the reference to the reference (reference) is changed to "ref (...)" in the string. Said.

-The updated Unicode processing mode drastically reduces the need for use UTF8: in Perl version 5.6, the data is considered Unicode, depending on whether the operation is in "use UTF8" and the valid scope of the compilation command; Now, Perl 5.8 directly links the "Unicode nature" to the data. Therefore, the use UTF8 is required only when the UTF-8 literal value (literal) is used within the program code. (In the absence of "use UTF8", the literal value is still treated as byte in order to maintain compatibility with existing command drafts.)

-vms:socket Extension Module dynamic, Alpha presets using IEEE floating-point numbers
-The Socket extension module is changed to dynamic loading on the VMS platform; This can cause problems in very old versions of VMS.
-OpenVMS Alpha is currently preset using IEEE floating-point numbers format. For the reasons and details of this, please see Readme.vms.

[Change with words]
-The "io rule (IO discipline) in the third edition of the Camel Book (Programming Perl, Perl programming) is now called the"io layer (IO layer).

[Not recommended]
-Dump ():
The function of the dump instruction is currently considered void.

-5.005 Multi-threading mode has not been recommended for use
Please use the new "interpreter multithreading" mode.

-Virtual Hash (Pseudohash):
The virtual hash syntax for the user level will be removed and changed to a more concise operation interface. In addition, the internal implementation must be changed because it slows down the access speed of the general hash.

-Contaminated (tainted) data in the "Exec (serial)" and "System (serial)" Parameters:
This will trigger a warning message at this time, but will become fatal in future releases.

-TR///C, tr///u:
The two operating interfaces were an accident; Please use Pack ("C0", ...) and pack ("U0", ...).

[Known issues]
-AmigaOS is unable to install the Perl 5.8.0.
-Compile Suite: bit code compilation and native code compilation are still problematic.
-Lvalue left-value function is still considered experimental.
-the intersection of local () and tie () The interoperability results are still not clearly defined.
-binding (tied) or magic (magical) arrays and hashes are not automatically generated (autovivify).
-Self-binding arrays and hashes, currently disabled.
---
to remind you again, please read pod/perldelta.pod, INSTALL, and README. platform.