Perl

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History

Name

The camel symbol

Overview

Features

Design

Applications

Implementation

Availability

Windows

Language structure

1. !/usr/bin/perl

Data types

• A scalar
  Scalar (computing)
  
  In computing, a scalar is a variable or field that can hold only one value at a time; as opposed to composite variables like array, List , object composition, etc....
   is a single value; it may be a number, a string
  String (computer science)
  
  In computer programming and some branches of mathematics, a string is an ordered sequence of symbols. These symbols are chosen from a predetermined set or alphabet....
  , or a reference
  Reference (computer science)
  
  In computer science, a reference is an object containing information about how to locate and access the particular data item, as opposed to containing the data itself....
  .
• An array
  Array
  
  In computer science, an array is a data structure consisting of a group of element s that are accessed by index . In most programming languages each element has the same data type and the array occupies a contiguous area of computer memory....
   is an ordered collection of scalars.
• A hash, or associative array
  Associative array
  
  An associative array is an abstract data type composed of a Collection of unique keys and a collection of values, where each key is associated with one value ....
  , is a map from strings to scalars; the strings are called keys, and the scalars are called values.
• A file handle is a map to a file, device, or pipe that is open for reading, writing, or both.
• A subroutine is a piece of code that may be passed arguments, be executed, and return data

1. This evaluates to true

$number2)

$answer = "The answer is $number1"; # Variable interpolation: The answer is 42 $price = 'This device costs $42'; # No interpolation in single quotes

$album = "It's David Bowie's \"Heroes\""; # literal quotes inside a string; $album = 'It\'s David Bowie\'s "Heroes"'; # same as above with single quotes; $album = q(It's David Bowie's "Heroes"); # the quote-like operators q and qq allow # almost any delimiter instead of quotes, to # avoid excessive backslashing

$multilined_string =<

Perl will convert strings into numbers and vice versa depending on the context in which they are used. In the following example, the strings $n and $m are treated as numbers when they are the arguments to the addition operator. This code prints the number '5', discarding non-numeric information for the operation, although the variable values remain the same. (The string concatenation operator is the period, not the + symbol.)

$n = '3 apples'; $m = '2 oranges'; print $n + $m;

Perl also has a boolean context that it uses in evaluating conditional statements. The following values all evaluate as false in Perl:

$false = 0; # the number zero $false = 0.0; # the number zero as a float $false = 0b0; # the number zero in binary $false = 0x0; # the number zero in hexadecimal $false = '0'; # the string zero $false = ""; # the empty string $false = undef; # the return value from undef

All other values are evaluated to true. This includes the odd self-describing literal string of "0 but true," which in fact is 0 as a number, but true when used as a boolean. (Any non-numeric string would also have this property, but this particular string is ignored by Perl with respect to numeric warnings.) A less-explicit but more conceptually portable version of this string is '0E0' or '0e0', which does not rely on characters being evaluated as 0, because '0E0' is literally "zero times ten to the zeroth power."

Evaluated boolean expressions also return scalar values. Although the documentation does not promise which particular true or false is returned (and thus cannot be relied on), many boolean operators return 1 for true and the empty-string for false (which evaluates to zero in a numeric context). The defined function tells if the variable has any value set. In the above examples, defined($false) is true for every value except undef.

If a specifically 1 or 0 result (as in C) is needed, an explicit conversion is thought by some authors to be required:

my $real_result = $boolean_result ? 1 : 0;

However, if it's known that the value is either 1 or undef, an implicit conversion can be used instead:

my $real_result = $boolean_result + 0;

A list is written by listing its elements, separated by commas, and enclosed by parentheses where required by operator precedence.

@scores = (32, 45, 16, 5);

It can be written many other ways as well, some straightforward and some less so:

1. An explicit and straightforward way

@scores = ('32', '45', '16', '5');

1. Equivalent to the above, but the qw quote-like operator saves typing of
2. quotes and commas and reduces visual clutter; almost any delimiter can be
3. used instead of parentheses

@scores = qw(32 45 16 5);

1. The split function returns a list of strings, which are extracted
2. from the expression using a regex template.
3. This may be useful for reading from a file of comma-separated values (CSV)

@scores = split /,/, '32,45,16,5';

1. It's also possible to use a postfix for operator and aliasing of
2. the $_ magic variable to the next value of the list during each
3. iteration; this is pointless here, but similar idioms are widely used
4. in some circumstances.

push @scores, $_ foreach 32, 45, 16, 5;

A hash may be initialized from a list of key/value pairs:

%favorite = ( joe => 'red', sam => 'blue' );

The => operator is equivalent to a comma, except that it assumes quotes around the preceding token if it is a bare identifier: (joe => 'red') is the same as ('joe' => 'red'). It can therefore be used to elide quote marks, improving readability.

Individual elements of a list are accessed by providing a numerical index, in square brackets. Individual values in a hash are accessed by providing the corresponding key, in curly braces. The $ sigil identifies the accessed element as a scalar.

$scores[2] # an element of @scores $favorite # a value in %favorite

Thus, a hash can also be specified by setting its keys individually:

$favorite = 'red'; $favorite = 'blue';

Multiple elements may be accessed by using the @ sigil instead (identifying the result as a list).

@scores[2, 3, 1] # three elements of @scores @favorite # two values in %favorite @favorite # same as above

The number of elements in an array can be obtained by evaluating the array in scalar context or with the help of the $# sigil. The latter gives the index of the last element in the array, not the number of elements. Note: the syntax highlighting

Syntax highlighting

Syntax highlighting is a feature of some text editors that displays text—especially source code—in different colors and typefaces according to the category of terms....
 in Wikipedia's software mistakenly considers some of the following code to be part of the comments.

$count = @friends; # Assigning to a scalar forces scalar context

$#friends; # The index of the last element in @friends $#friends+1; # Usually the number of elements in @friends is one more # than $#friends because the first element is at index 0, # not 1, unless the programmer reset this to a different # value, which most Perl manuals discourage.

There are a few functions that operate on entire hashes.

@names = keys %addressbook; @addresses = values %addressbook;

1. Every call to each returns the next key/value pair.
2. All values will be eventually returned, but their order
3. cannot be predicted.

while (($name, $address) = each %addressbook)

1. Similar to the above, but sorted alphabetically

foreach my $next_name (sort keys %addressbook)

Control structures

Perl has several kinds of control structures.

It has block-oriented control structures, similar to those in the C, Javascript

JavaScript

JavaScript is a scripting language widely used for client-side web development. It was the originating Programming language dialect of the ECMAScript standard....
, and Java

Java (programming language)

Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java ....
 programming languages. Conditions are surrounded by parentheses, and controlled blocks are surrounded by braces:

label while ( cond ) label while ( cond ) continue label for ( init-expr ; cond-expr ; incr-expr ) label foreach var ( list ) label foreach var ( list ) continue if ( cond ) if ( cond ) else if ( cond ) elsif ( cond ) else

Where only a single statement is being controlled, statement modifiers provide a more-concise syntax:

statement if cond ; statement unless cond ; statement while cond ; statement until cond ; statement foreach list ;

Short-circuit logical operators are commonly used to affect control flow at the expression level:

expr and expr expr && expr expr or expr expr || expr

(The "and" and "or" operators are similar to && and || but have lower precedence

Precedence

Precedence is a simple ordering, based on either importance or sequence; it may refer to one of the following:* Message precedence of military communications traffic...
, which makes it easier to use them to control entire statements.)

The flow control keywords next (corresponding to C's continue), last (corresponding to C's break), return, and redo are expressions, so they can be used with short-circuit operators.

Perl also has two implicit looping constructs, each of which has two forms:

results = grep list results = grep expr, list results = map list results = map expr, list

grep returns all elements of list for which the controlled block or expression evaluates to true. map evaluates the controlled block or expression for each element of list and returns a list of the resulting values. These constructs enable a simple functional programming

Functional programming

In computer science, functional programming is a programming paradigm that treats computation as the evaluation of function s and avoids program state and immutable object data....
 style.

Up until the 5.10.0 release, there was no switch statement

Switch statement

In computer programming, a switch statement is a type of control Statement that exists in most modern imperative programming languages . Its purpose is to allow the value of a variable or expression to control the flow of program execution....
 in Perl 5. From 5.10.0 onward, a multi-way branch statement called given/when is available, which takes the following form:

given ( expr )

Syntactically, this structure behaves similarly to switch statement

Switch statement

In computer programming, a switch statement is a type of control Statement that exists in most modern imperative programming languages . Its purpose is to allow the value of a variable or expression to control the flow of program execution....
s found in other languages, but with a few important differences. The largest is that unlike switch/case structures, given/when statements break execution after the first successful branch, rather than waiting for explicitly defined break commands. Conversely, explicit continues are instead necessary to emulate switch behavior.

For those not using the 5.10.0 release, the Perl documentation describes a half-dozen ways to achieve the same effect by using other control structures. There is also a module, which provides functionality modeled on the forthcoming Perl 6

Perl 6

Perl 6 is a planned major revision to the Perl programming language. It is a language specification which introduces elements of many modern and historical languages....
 re-design. It is implemented using a source filter, so its use is unofficially discouraged.

Perl includes a goto label statement, but it is rarely used. Situations where a goto is called for in other languages don't occur as often in Perl because of its breadth of flow control options.

There is also a goto &sub statement that performs a tail call

Tail call

A tail call is a call to a subroutine which is followed by a return to the calling code. Such a call is said to be in tail position. If a subroutine performs a tail call to itself, it is called tail recursion....
. It terminates the current subroutine and immediately calls the specified sub. This is used in situations where a caller can perform more-efficient stack

Call stack

In computer science, a call stack is a dynamic Stack data structure that stores information about the active subroutines of a computer program....
 management than Perl itself (typically because no change to the current stack is required), and in deep recursion, tail calling can have substantial positive impact on performance because it avoids the overhead of scope/stack management on return.

Subroutines

Subroutine

Subroutine

In computer science, a subroutine or subprogram is a portion of computer code within a larger computer program, which performs a specific task and is relatively independent of the remaining code....
s are defined with the sub keyword and are invoked simply by naming them. If the subroutine in question has not yet been declared, invocation requires either parentheses after the function name or an ampersand (&) before it. But using & without parentheses will also implicitly pass the arguments of the current subroutine to the one called, and using & with parentheses will bypass prototypes.

1. Calling a subroutine

1. Parentheses are required here if the subroutine is defined later in the code

foo; &foo; # (this also works, but has other consequences regarding arguments passed to the subroutine)

1. Defining a subroutine

sub foo

foo; # Here parentheses are not required

A list of arguments may be provided after the subroutine name. Arguments may be scalars, lists, or hashes.

foo $x, @y, %z; The parameters to a subroutine do not need to be declared as to either number or type; in fact, they may vary from call to call. Any validation of parameters must be performed explicitly inside the subroutine.

Arrays are expanded to their elements; hashes are expanded to a list of key/value pairs; and the whole lot is passed into the subroutine as one flat list of scalars.

Whatever arguments are passed are available to the subroutine in the special array @_. The elements of @_ are aliased to the actual arguments; changing an element of @_ changes the corresponding argument.

Elements of @_ may be accessed by subscripting it in the usual way.

$_[0], $_[1]

However, the resulting code can be difficult to read, and the parameters have pass-by-reference

Evaluation strategy

In computer science, an evaluation strategy is a set of rules for determining the evaluation of expression in a programming language. Emphasis is typically placed on subprogram or operators ? an evaluation strategy defines when and in what order the arguments to a function are evaluated, when they are substituted into the function, and wha...
 semantics, which may be undesirable.

One common idiom is to assign @_ to a list of named variables.

my ($x, $y, $z) = @_;

This provides mnemonic parameter names and implements pass-by-value

Evaluation strategy

In computer science, an evaluation strategy is a set of rules for determining the evaluation of expression in a programming language. Emphasis is typically placed on subprogram or operators ? an evaluation strategy defines when and in what order the arguments to a function are evaluated, when they are substituted into the function, and wha...
 semantics. The my keyword indicates that the following variables are lexically scoped to the containing block.

Another idiom is to shift parameters off of @_. This is especially common when the subroutine takes only one argument or for handling the $self argument in object-oriented modules.

my $x = shift;

Subroutines may assign @_ to a hash to simulate named arguments; this is recommended in Perl Best Practices for subroutines that are likely to ever have more than three parameters.

sub function1 function1( x => 23 );

Subroutines may return values.

return 42, $x, @y, %z;

If the subroutine does not exit via a return statement, then it returns the last expression evaluated within the subroutine body. Arrays and hashes in the return value are expanded to lists of scalars, just as they are for arguments.

The returned expression is evaluated in the calling context of the subroutine; this can surprise the unwary.

sub list sub array

$x = list; # returns 6 - last element of list $x = array; # returns 3 - number of elements in list @x = list; # returns (4, 5, 6) @x = array; # returns (4, 5, 6)

A subroutine can discover its calling context with the wantarray function.

sub either

$x = either; # returns "Oranges" @x = either; # returns (1, 2)

Regular expressions

The Perl language includes a specialized syntax for writing regular expression

Regular expression

In computing, regular expressions provide a concise and flexible means for identifying strings of text of interest, such as particular characters, words, or patterns of characters....
s (RE, or regexes), and the interpreter contains an engine for matching strings to regular expressions. The regular-expression engine uses a backtracking

Backtracking

Backtracking is a general algorithm for finding all solutions to some computational problem, that incrementally builds candidates to the solutions, and abandons each partial candidate c as soon as it determines that c cannot possibly be completed to a valid solution ....
 algorithm, extending its capabilities from simple pattern matching to string capture and substitution. The regular-expression engine is derived from regex written by Henry Spencer

Henry Spencer

Henry Spencer is a Canada computer programmer and space enthusiast. He wrote 'regex', a widely-used Library for regular expressions, and co-wrote C News, a Usenet server program....
.

The Perl regular-expression syntax was originally taken from Unix Version 8 regular expressions. However, it diverged before the first release of Perl and has since grown to include far more features. Many other languages and applications are now adopting Perl compatible regular expressions over POSIX

POSIX

POSIX or "Portable Operating System Interface" is the collective name of a family of related standardizations specified by the Institute of Electrical and Electronics Engineers to define the application programming interface , along with shell and utilities interfaces for software compatible with variants of the Unix operating system, altho...
 regular expressions, such as PHP

PHP

PHP is a scripting language originally designed for producing dynamic web pages. It has evolved to include a command line interface capability and can be used in Standalone software Graphical user interface....
, Ruby, Java

Java (programming language)

Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java ....
, Microsoft's .NET Framework

.NET Framework

The Microsoft .NET Framework is a software framework that is available with several Microsoft Windows operating systems. It includes a large Library of coded solutions to prevent common programming problems and a virtual machine that manages the execution of programs written specifically for the Software framework....
, and the Apache HTTP server

Apache HTTP Server

The Apache HTTP Server, commonly referred to simply as Apache , is a web server notable for playing a key role in the initial growth of the World Wide Web....
.

Regular-expression syntax is extremely compact, owing to history. The first regular-expression dialects were only slightly more expressive than globs, and the syntax was designed so that an expression would resemble the text that it matches. This meant using no more than a single punctuation character or a pair of delimiting characters to express the few supported assertions. Over time, the expressiveness of regular expressions grew tremendously, but the syntax design was never revised and continues to rely on punctuation. As a result, regular expressions can be cryptic and extremely dense.

Uses

The m// (match) operator introduces a regular-expression match. (If it is delimited by slashes, as in all of the examples here, then the leading m may be omitted for brevity. If the m is present, as in all of the following examples, other delimiters can be used in place of slashes.) In the simplest case, an expression such as

$x =~ /abc/;

evaluates to true if and only if

If and only if

If and only if, in logic and fields that rely on it such as mathematics and philosophy, is a biconditional logical connective between statements....
 the string $x matches the regular expression abc.

The s/// (substitute) operator, on the other hand, specifies a search-and-replace operation:

$x =~ s/abc/aBc/; # upcase the b

Another use of regular expressions is to specify delimiters for the split function:

@words = split /,/, $line;

The split function creates a list of the parts of the string that are separated by matches of the regular expression. In this example, a line is divided into a list of its comma-separated parts, and this list is then assigned to the @words array.

Syntax

Modifiers

Perl regular expressions can take modifiers. These are single-letter suffixes that modify the meaning of the expression:

$x =~ /abc/i; # case-insensitive pattern match $x =~ s/abc/aBc/g; # global search and replace

Because the compact syntax of regular expressions can make them dense and cryptic, the /x modifier was added in Perl to help programmers write more-legible regular expressions. It allows programmers to place whitespace and comments inside regular expressions:

$x =~ / a # match 'a' . # followed by any character c # then followed by the 'c'character /x;

Capturing

Portions of a regular expression may be enclosed in parentheses; corresponding portions of a matching string are captured. Captured strings are assigned to the sequential built-in variables $1, $2, $3, ..., and a list of captured strings is returned as the value of the match.

$x =~ /a(.)c/; # capture the character between 'a' and 'c'

Captured strings $1, $2, $3, ... can be used later in the code.

Perl regular expressions also allow built-in or user-defined functions apply to the captured match, by using the /e modifier:

$x = "Oranges"; $x =~ s/(ge)/uc($1)/e; # OranGEs $x .= $1; # append $x with the contents of the match in the previous statement: OranGEsge

Perl is widely favored for database applications. Its text-handling facilities are useful for generating SQL

SQL

SQL is a database computer language designed for the retrieval and management of data in relational database management systems , database schema creation and modification, and database object access control management....
 queries; arrays, hashes, and automatic memory management make it easy to collect and process the returned data.

In early versions of Perl, database interfaces were created by relinking the interpreter with a client-side database library. This was sufficiently difficult that it was done for only a few of the most-important and most widely used databases, and it restricted the resulting perl executable to using just one database interface at a time.

In Perl 5, database interfaces are implemented by Perl DBI

Perl DBI

Perl DBI is the most common database interface for the Perl programming language.DBI was specified by Tim Bunce, in collaboration with others, starting in 1992, and is currently maintained across the Internet as a CPAN module in accordance with the Open Source model....
 modules. The DBI (Database Interface) module presents a single, database-independent interface to Perl applications, while the DBD (Database Driver) modules handle the details of accessing some 50 different databases; there are DBD drivers for most ANSI

American National Standards Institute

The American National Standards Institute or ANSI is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States....
 SQL

SQL

SQL is a database computer language designed for the retrieval and management of data in relational database management systems , database schema creation and modification, and database object access control management....
 databases.

DBI provides caching for database handles and queries, which can greatly improve performance in long-lived execution environments such as mod_perl

Mod perl

mod_perl is an optional module for the Apache HTTP server. It embeds a Perl Interpreter into the Apache server, so that dynamic content produced by Perl Scripting language can be served in response to incoming requests, without the significant overhead of re-launching the Perl interpreter for each request....
, helping high-volume systems avert load spikes as in the Slashdot effect

Slashdot effect

The Slashdot effect, also known as slashdotting, is the phenomenon of a popular website linking to a smaller site, causing the smaller site to slow down or even temporarily close due to the increased traffic....
.

The Computer Language Benchmarks Game compares the performance of implementations of typical programming problems in several programming languages. The submitted Perl implementations were typically toward the high end of the memory-usage spectrum and had varied speed results. Perl's performance in the benchmarks game is typical for interpreted languages and places it toward the lead in that group.

Large Perl programs start slower than similar programs in compiled languages because perl has to compile the source every time it runs. In a talk at the YAPCEurope 2005 conference and subsequent article "A Timely Start," Jean-Louis Leroy found that his Perl programs took much longer to run than he expected because the perl interpreter spent much of the time finding modules because of his over-large include path. Unlike Java, Python, and Ruby, Perl has only experimental support for pre-compiling. Therefore Perl programs pay this overhead penalty on every execution. The run phase of typical programs is long enough that amortized startup time is not substantial, but results in benchmarks that measure very short execution times are likely to be skewed.

A number of tools have been introduced to improve this situation. The first such tool was Apache's mod_perl

Mod perl

mod_perl is an optional module for the Apache HTTP server. It embeds a Perl Interpreter into the Apache server, so that dynamic content produced by Perl Scripting language can be served in response to incoming requests, without the significant overhead of re-launching the Perl interpreter for each request....
, which sought to address one of the most-common reasons that small Perl programs were invoked rapidly: CGI

Common Gateway Interface

The Common Gateway Interface is a Standardization Protocol for interfacing external application software with an Server , commonly a web server....
 Web

World Wide Web

The World Wide Web is a very large set of interlinked hypertext documents accessed via the Internet. With a Web browser, one can view Web pages that may contain writing, s, videos, and other multimedia and navigate between them using hyperlinks....
 development. ActivePerl

ActiveState

ActiveState is a Canadian proprietary software company headquartered in Vancouver, British Columbia that develops, sells, and supports cross-platform software development tools for dynamic programming language such as Perl, PHP, Python , Ruby , and Tcl, as well as Software distribution and enterprise services....
, via Microsoft ISAPI

ISAPI

The Internet Server Application Programming Interface is an N-tier Application programming interface of Internet Information Services , Microsoft's collection of Microsoft Windows-based web server services....
, provides similar performance improvements.

Once Perl code is compiled, there is additional overhead during the execution phase that typically isn't present for programs written in compiled languages such as C or C++. Examples of such overhead include bytecode interpretation, reference-counting memory management, and dynamic type checking.

Optimizing

At the 2000 Perl Conference

O'Reilly Open Source Convention

The O'Reilly Open Source Convention is an annual Convention for the discussion of free and open source software. It is organized by the publisher O'Reilly Media and is held each summer in the United States....
, Jon Orwant made a case for a major new language initiative. This led to a decision to begin work on a redesign of the language, to be called Perl 6. Proposals for new language features were solicited from the Perl community at large, and more than 300 RFCs

Request for Comments

In computer network engineering, a request for comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems....
 were submitted.

Larry Wall

Larry Wall

Larry Wall is a programmer and author, most widely known for his creation of the Perl programming language in 1987....
 spent the next few years digesting the RFCs and synthesizing them into a coherent framework for Perl 6. He has presented his design for Perl 6 in a series of documents called "apocalypses," which are numbered to correspond to chapters in Programming Perl

Programming Perl

Programming Perl,ISBN 0-596-00027-8,best known as the Camel Book among programmers, is a book about writing programs using the Perl programming language....
 ("The Camel Book"). The current, not-yet-finalized specification of Perl 6 is encapsulated in design documents called Synopses, which are numbered to correspond to Apocalypses.

Perl 6 is not intended to be backward compatible, although there will be a compatibility mode.

Thesis work by Bradley M. Kuhn

Bradley M. Kuhn

Bradley M. Kuhn is a free software activist from the United States. Kuhn is currently the FLOSS Community Liaison and Technology Director of Software Freedom Law Center and president of the Software Freedom Conservancy....
, overseen by Larry Wall, considered the possible use of the Java virtual machine

Java Virtual Machine

A Java Virtual Machine is a set of computer software programs and data structures which use a virtual machine model for the execution of other computer programs and Scripting language....
 as a runtime for Perl. Kuhn's thesis showed this approach to be problematic, and in 2001, it was decided that Perl 6 would run on a cross-language virtual machine

Virtual machine

In computer science, a virtual machine is a software implementation of a machine that executes programs like a real machine.Definitions...
 called Parrot

Parrot virtual machine

Parrot is a register machine virtual machine being developed using the C and intended to run dynamic languages efficiently. It uses just-in-time compilation for speed to reduce the interpretation overhead....
. This will mean that other languages targeting the Parrot will gain native access to CPAN

CPAN

CPAN, the Comprehensive Perl Archive Network, is an archive of over 14,800 modules of software written in Perl, as well as documentation for it....
, allowing some level of cross-language development.

In 2005, Audrey Tang

Audrey Tang

Audrey Tang is a Taiwanese people free software programmer, who has been described as one of the "ten greats of Taiwanese computing."...
 created the pugs

Pugs

Pugs is a compiler and interpreter for the Perl 6 programming language, started on February 1 2005 by Audrey Tang....
 project, an implementation of Perl 6 in Haskell

Haskell (programming language)

Haskell is a standardized, purely functional programming language with non-strict programming language, named after logician Haskell Curry. The goals of the language are described as:...
. This was, and continues to act as, a test platform for the Perl 6 language (separate from the development of the actual implementation) allowing the language designers to explore. The pugs project spawned an active Perl/Haskell cross-language community centered around the freenode

Freenode

freenode, formerly known as Open Projects Network, is a popular Internet Relay Chat computer network used to discuss peer-directed projects....
 #perl6 irc channel.

A number of features in the Perl 6 language now show similarities to Haskell, and Perl 6 has been embraced by the Haskell community as a potential scripting language.

, Perl 6, Parrot, and pugs are under active development, and a new module for Perl 5 called v6

V6 (Perl)

v6 is a Perl module which runs under Perl version 5, and transforms Perl 6 code into Perl 5 code on the fly. To quote the release notes:...
 allows some Perl 6 code to run directly on top of Perl 5.

Development of Perl 5 is also continuing. Perl 5.10 was released in December 2007, with some new features influenced by the design of Perl 6.

Perl's culture and community has developed alongside the language itself. Usenet

Usenet

Usenet, a portmanteau of "user" and "network", is a worldwide distributed Internet discussion system. It evolved from the general purpose UUCP architecture of the same name....
 was the first public venue in which Perl was introduced, but over the course of its evolution, Perl's community was shaped by the growth of broadening Internet-based services including the introduction of the World Wide Web. The community that surrounds Perl was, in fact, the topic of Larry Wall's first "State of the Onion" talk.

State of the Onion

Pastimes

JAPHs

Perl golf

Obfuscation

Poetry

CPAN Acme

• Learning Perl
  Learning Perl
  
  Learning Perl, also known as the llama book, is a tutorial book for the Perl programming language, and is published by O'Reilly Media....
  , Fifth Edition (the Llama book), ISBN 0-596-52010-6
• Perl Cookbook
  Perl Cookbook
  
  The Perl Cookbook, ISBN 0-596-00313-7, is a book containing solutions to common short tasks in Perl. Each chapter covers a particular topic area and is divided into around a dozen recipes each on a particular problem ....
  , ISBN 0-596-00313-7
• Programming Perl
  Programming Perl
  
  Programming Perl,ISBN 0-596-00027-8,best known as the Camel Book among programmers, is a book about writing programs using the Perl programming language....
   (the Camel book), ISBN 0-596-00027-8
• published 1996-2006 was the leading publication for and about Perl Programming during this time.

• Autovivification
  Autovivification
  
  Autovivification is a unique feature of the Perl programming language involving the dynamic creation of data structures. Autovivification is the automatic creation of a reference when an undefined value is dereferenced....
  
• Comparison of programming languages
  Comparison of programming languages
  
  Programming languages are used for controlling the behavior of a machine . Like natural languages, programming languages conform to rules for syntax and semantics....
  
• Just another Perl hacker
  Just another Perl hacker
  
  Just another Perl hacker, or JAPH, typically refers to a Perl program which prints "Just another Perl hacker," . Short JAPH programs are often used as signature block in online Internet forum, or as T-shirt designs....
  
• Perl Data Language
  Perl Data Language
  
  PDL is a set of array programming extensions to the Perl.PDL is an extension to Perl v5, intended for scientific and other data intensive programming tasks....
  
• Perl Object Environment
  Perl Object Environment
  
  The Perl Object Environment or POE is a Library of Perl modules written in the Perl programming language by Rocco Caputo et alia.From CPAN:...
  
• PerlScript
  PerlScript
  
  PerlScript was initially solely an ActiveX Scripting Engine produced by the company ActiveState for use with Microsoft Internet Information Services that allows for programmers to use Perl-based code in addition to, or in place of, VBScript or JScript in the context of web servers running the Active Server Pages protocol....
  
• Plain Old Documentation
  Plain Old Documentation
  
  Plain Old Documentation, abbreviated pod, is a simplemarkup language used to document the Perl programming language....
  

• —Official Perl website