HOME

TheInfoList




Perl is a family of two
high-level High-level and low-level, as technical terms, are used to classify, describe and point to specific Objective (goal), goals of a systematic operation; and are applied in a wide range of contexts, such as, for instance, in domains as widely varied as ...
, general-purpose, interpreted,
dynamic programming language In computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its computation as well as practical techniques for their application. Computer science is the study of Alg ...
s. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was officially changed to Raku in October 2019. Though Perl is not officially an acronym, there are various
backronym A backronym, or bacronym, is an acronym formed from a word that existed prior to the invention of the backronym. Unlike a typical acronym, in which a new word is constructed from a phrase, the phrase corresponding to the backronym is selected to fi ...
s in use, including "Practical Extraction and Reporting Language". Perl was developed by
Larry Wall Larry Arnold Wall (born September 27, 1954) is an American computer programmer and author. He created the Perl programming language. Personal life Wall grew up in Los Angeles and then Bremerton, Washington, before starting higher education at Sea ...
in 1987 as a general-purpose
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser Multi-user software is computer software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to ...

Unix
scripting language A scripting language or script language is a programming language A programming language is a formal language comprising a Instruction set architecture, set of instructions that produce various kinds of Input/output, output. Programming language ...
to make report processing easier. Since then, it has undergone many changes and revisions. Raku, which began as a redesign of Perl 5 in 2000, eventually evolved into a separate language. Both languages continue to be developed independently by different development teams and liberally borrow ideas from each other. The Perl languages borrow features from other programming languages including C,
shell script A shell script is a computer program designed to be run by the Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file mani ...
( sh),
AWK AWK (''awk'') is a domain-specific languageA domain-specific language (DSL) is a computer languageA computer language is a method of communication with a computer A computer is a machine that can be programmed to carry out sequences of ari ...
, and
sed sed ("stream editor") is a Unix Unix (; trademarked as UNIX) is a family of Computer multitasking, multitasking, multiuser computer operating systems that derive from the original AT&T Corporation, AT&T Unix, whose development started in th ...
; They provide text processing facilities without the arbitrary data-length limits of many contemporary Unix command line tools. Perl 5 gained widespread popularity in the late 1990s as a CGI scripting language, in part due to its powerful
regular expression A regular expression (shortened as regex or regexp; also referred to as rational expression) is a sequence of that specifies a ''search ''. Usually such patterns are used by s for "find" or "find and replace" operations on , or for input val ...
and
string String or strings may refer to: *String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other objects Arts, entertainment, and media Films * Strings (1991 film), ''Strings'' (1991 fil ...
parsing Parsing, syntax analysis, or syntactic analysis is the process of analyzing a string String or strings may refer to: *String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other obje ...

parsing
abilities. In addition to CGI, Perl 5 is used for
system administration A system administrator, or sysadmin, or admin is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems A computer is a machine A machine is a man-made device that uses power to apply ...
, network programming, finance,
bioinformatics Bioinformatics () is an field that develops methods and s for understanding data, in particular when the data sets are large and complex. As an interdisciplinary field of science, bioinformatics combines , , , and to analyze and interpret ...

bioinformatics
, and other applications, such as for
GUI#REDIRECT graphical user interface The graphical user interface (GUI "UI" by itself is still usually pronounced . or ) is a form of user interface that allows User (computing), users to Human–computer interaction, interact with electronic devic ...
s. It has been nicknamed "the Swiss Army chainsaw of scripting languages" because of its flexibility and power, and also its ugliness. In 1998, it was also referred to as the "
duct tape Duct tape (also called duck tape, from the material it was originally made of) is cloth- or scrim-backed pressure-sensitive tape, often coated with polyethylene. There are a variety of constructions using different backings and adhesives, and the ...
that holds the
Internet The Internet (or internet) is the global system of interconnected s that uses the (TCP/IP) to communicate between networks and devices. It is a ' that consists of private, public, academic, business, and government networks of local to ...

Internet
together," in reference to both its ubiquitous use as a glue language and its perceived inelegance. Perl is a highly expressive programming language: source code for a given algorithm can be short and highly compressible.


Name

Perl was originally named "Pearl". Wall wanted to give the language a short name with positive connotations. Wall discovered the existing
PEARL A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle (mollusc), mantle) of a living animal shell, shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pe ...
programming language before Perl's official release and changed the spelling of the name. When referring to the language, the name is capitalized: ''Perl''. When referring to the program itself, the name is uncapitalized (''perl'') because most Unix-like file systems are case-sensitive. Before the release of the first edition of ''
Programming Perl ''Programming Perl'', best known as the Camel Book among programmers, is a book about writing programs using the Perl programming language, revised as several editions (1991-2012) to reflect major language changes since Perl version 4. Editions ha ...
'', it was common to refer to the language as ''perl''. Randal L. Schwartz, however, capitalized the language's name in the book to make it stand out better when typeset. This case distinction was subsequently documented as canonical. The name is occasionally expanded as a
backronym A backronym, or bacronym, is an acronym formed from a word that existed prior to the invention of the backronym. Unlike a typical acronym, in which a new word is constructed from a phrase, the phrase corresponding to the backronym is selected to fi ...
: ''Practical Extraction and Report Language'' and Wall's own ''Pathologically Eclectic Rubbish Lister'' which is in the
manual page A man page (short for manual page) is a form of software documentation Software documentation is written text or illustration that accompanies computer software or is embedded in the source code. The documentation either explains how the softwa ...
for perl.


History


Early versions

Larry Wall Larry Arnold Wall (born September 27, 1954) is an American computer programmer and author. He created the Perl programming language. Personal life Wall grew up in Los Angeles and then Bremerton, Washington, before starting higher education at Sea ...
began work on Perl in 1987, while working as a programmer at
Unisys Unisys Corporation is an American Multinational corporation, multinational information technology (IT) services and consulting company headquartered in Blue Bell, Pennsylvania, Blue Bell, Pennsylvania. It is the legacy proprietor of the Burroughs ...
, and version 1.0 was released to the comp.sources.unix
newsgroup A Usenet newsgroup is a Software repository, repository usually within the Usenet system, for messages Posting style, posted from users in different locations using the Internet. They are discussion groups and are not devoted to publishing news. N ...
on February 1, 1988. The language expanded rapidly over the next few years. Perl 2, released in 1988, featured a better regular expression engine. Perl 3, released in 1989, added support for
binary data Binary data is data whose unit can take on only two possible states, traditionally labeled as 0 and 1 in accordance with the binary numeral system and Boolean algebra. Binary data occurs in many different technical and scientific fields, where it ...
streams. Originally, the only documentation for Perl was a single lengthy
man page A man page (short for manual page) is a form of software documentation Software documentation is written text or illustration that accompanies computer software or is embedded in the source code. The documentation either explains how the softwa ...
. In 1991, ''Programming Perl'', known to many Perl programmers as the "Camel Book" because of its cover, was published and became the ''de facto'' reference for the language. At the same time, the Perl version number was bumped to 4, not to mark a major change in the language but to identify the version that was well documented by the book.


Early Perl 5

Perl 4 went through a series of
maintenance release A maintenance release (also minor release or Maintenance Pack or MP) is a release of a product that does not add new features or content. For instance, in computer software, maintenance software release, releases are typically intended to solve mino ...
s, culminating in Perl 4.036 in 1993, whereupon Wall abandoned Perl 4 to begin work on Perl 5. Initial design of Perl 5 continued into 1994. The ''perl5-porters''
mailing list A mailing list is a collection of names and addresses used by an individual or an organization to send material to multiple recipients. The term is often extended to include the people subscribed to such a list, so the group of subscribers is refe ...
was established in May 1994 to coordinate work on porting Perl 5 to different platforms. It remains the primary forum for development, maintenance, and porting of Perl 5. Perl 5.000 was released on October 17, 1994. It was a nearly complete rewrite of the interpreter, and it added many new features to the language, including objects,
references Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a ''name'' ...
, lexical (my) variables, and
modules Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a syst ...
. Importantly, modules provided a mechanism for extending the language without modifying the interpreter. This allowed the core interpreter to stabilize, even as it enabled ordinary Perl programmers to add new language features. Perl 5 has been in active development since then. Perl 5.001 was released on March 13, 1995. Perl 5.002 was released on February 29, 1996 with the new prototypes feature. This allowed module authors to make
subroutine In computer programming Computer programming is the process of designing and building an executable computer program to accomplish a specific computing result or to perform a particular task. Programming involves tasks such as analysis, generat ...
s that behaved like Perl builtins. Perl 5.003 was released June 25, 1996, as a security release. One of the most important events in Perl 5 history took place outside of the language proper and was a consequence of its module support. On October 26, 1995, the Comprehensive Perl Archive Network (CPAN) was established as a repository for the Perl language and
Perl module A Perl module is a discrete component of software Software is a collection of instructions that tell a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Mod ...

Perl module
s; as of May 2017, it carries over 185,178 modules in 35,190 distributions, written by more than 13,071 authors, and is mirrored worldwide at more than 245 locations. Perl 5.004 was released on May 15, 1997, and included, among other things, the UNIVERSAL package, giving Perl a base object from which all
classes Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
were automatically derived and the ability to require versions of modules. Another significant development was the inclusion of the
CGI.pm CGI.pm is a large and once widely used Perl moduleA Perl module is a discrete component of software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to work. This is ...
module, which contributed to Perl's popularity as a CGI scripting language. Perl 5.004 added support for
Microsoft Windows Microsoft Windows, commonly referred to as Windows, is a group of several families, all of which are developed and marketed by . Each family caters to a certain sector of the computing industry. Active Microsoft Windows families include an ...
, Plan 9,
QNX QNX ( or ) is a commercial Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Sing ...
, and
AmigaOS AmigaOS is a family of proprietary native operating system An operating system (OS) is system software that manages computer hardware, computer software, software resources, and provides common daemon (computing), services for computer program ...

AmigaOS
. Perl 5.005 was released on July 22, 1998. This release included several enhancements to the
regex A regular expression (shortened as regex or regexp; also referred to as rational expression) is a sequence of Character (computing), characters that specifies a ''search pattern matching, pattern''. Usually such patterns are used by string-sea ...
engine, new hooks into the backend through the B::* modules, the qr// regex quote operator, a large selection of other new core modules, and added support for several more operating systems, including
BeOS BeOS is an operating system An operating system (OS) is system software System software is software designed to provide a platform for other software. Examples of system software include operating systems like macOS macOS (; previously ...
.


2000–2020

Perl 5.6 was released on March 22, 2000. Major changes included
64-bit In computer architecture In computer engineering Computer engineering (CoE or CpE) is a branch of engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other it ...
support,
Unicode Unicode, formally the Unicode Standard, is an information technology standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requireme ...

Unicode
string representation, support for files over 2 GiB, and the "our" keyword. When developing Perl 5.6, the decision was made to switch the versioning scheme to one more similar to other open source projects; after 5.005_63, the next version became 5.5.640, with plans for development versions to have odd numbers and stable versions to have even numbers. In 2000, Wall put forth a call for suggestions for a new version of Perl from the community. The process resulted in 361 RFC (request for comments) documents that were to be used in guiding development of Perl 6. In 2001, work began on the "Apocalypses" for Perl 6, a series of documents meant to summarize the change requests and present the design of the next generation of Perl. They were presented as a digest of the RFCs, rather than a formal document. At this point, Perl 6 existed only as a description of a language. Perl 5.8 was first released on July 18, 2002, and had nearly yearly updates since then. Perl 5.8 improved Unicode support, added a new I/O implementation, added a new thread implementation, improved numeric accuracy, and added several new modules. As of 2013 this version still remains the most popular version of Perl and is used by Red Hat 5, Suse 10, Solaris 10, HP-UX 11.31 and AIX 5. In 2004, work began on the "Synopses"documents that originally summarized the Apocalypses, but which became the specification for the Perl 6 language. In February 2005,
Audrey Tang Audrey Tang ( zh, t=唐鳳, p=Táng Fèng; born 18 April 1981) is a Taiwanese free software Free software (or libre software) is computer software Software is a collection of Instruction (computer science), instructions and data (compu ...

Audrey Tang
began work on Pugs, a Perl 6 interpreter written in Haskell. This was the first concerted effort towards making Perl 6 a reality. This effort stalled in 2006. PONIE is an acronym for Perl On New Internal Engine. The PONIE Project existed from 2003 until 2006 and was to be a bridge between Perl 5 and Perl 6. It was an effort to rewrite the Perl 5 interpreter to run on
Parrot Parrots, also known as psittacines , are bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class ...
, the Perl 6 virtual machine. The goal was to ensure the future of the millions of lines of Perl 5 code at thousands of companies around the world. The PONIE project ended in 2006 and is no longer being actively developed. Some of the improvements made to the Perl 5 interpreter as part of PONIE were folded into that project. On December 18, 2007, the 20th anniversary of Perl 1.0, Perl 5.10.0 was released. Perl 5.10.0 included notable new features, which brought it closer to Perl 6. These included a
switch statement In computer programming language A programming language is a formal language comprising a set of instructions that produce various kinds of output. Programming languages are used in computer programming Computer programming is the proces ...
(called "given"/"when"), regular expressions updates, and the smart match operator'' (~~). Around this same time, development began in earnest on another implementation of Perl 6 known as Rakudo Perl, developed in tandem with the
Parrot virtual machine Parrot is discontinued software that implements a register-based process virtual machine designed to run dynamic languages efficiently. It is possible to compile Parrot assembly language and Parrot intermediate representation (PIR, an intermedia ...
. As of November 2009, Rakudo Perl has had regular monthly releases and now is the most complete implementation of Perl 6. A major change in the development process of Perl 5 occurred with Perl 5.11; the development community has switched to a monthly release cycle of development releases, with a yearly schedule of stable releases. By that plan, bugfix point releases will follow the stable releases every three months. On April 12, 2010, Perl 5.12.0 was released. Notable core enhancements include new package NAME VERSION syntax, the Yada Yada operator (intended to mark placeholder code that is not yet implemented), implicit strictures, full
Y2038 The Year 2038 problem (also called Y2038, Epochalypse, Y2K38, Y2038 error, Y2K38 superbug or Unix Y2K) relates to representing time in many digital systems as the number of seconds passed since 00:00:00 UTC on 1 January 1970 and storing it as a ...
compliance, regex conversion overloading,
DTrace DTrace is a comprehensive dynamic framework originally created by for and application problems on production systems in real time. Originally developed for , it has since been released under the free (CDDL) in and its descendant , and has b ...
support, and
Unicode Unicode, formally the Unicode Standard, is an information technology standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requireme ...

Unicode
5.2. On January 21, 2011, Perl 5.12.3 was released; it contains updated modules and some documentation changes. Version 5.12.4 was released on June 20, 2011. The latest version of that branch, 5.12.5, was released on November 10, 2012. On May 14, 2011, Perl 5.14 was released with
JSON JSON (JavaScript Object Notation, pronounced ; also ) is an open standard An open standard is a standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm ...
support built-in. On May 20, 2012, Perl 5.16 was released. Notable new features include the ability to specify a given version of Perl that one wishes to emulate, allowing users to upgrade their version of Perl, but still run old scripts that would normally be incompatible. Perl 5.16 also updates the core to support
Unicode Unicode, formally the Unicode Standard, is an information technology standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requireme ...

Unicode
6.1. On May 18, 2013, Perl 5.18 was released. Notable new features include the new dtrace hooks, lexical subs, more CORE:: subs, overhaul of the hash for security reasons, support for Unicode 6.2. On May 27, 2014, Perl 5.20 was released. Notable new features include subroutine signatures, hash slices/new slice syntax, postfix dereferencing (experimental), Unicode 6.3, using consistent random number generator. Some observers credit the release of Perl 5.10 with the start of the Modern Perl movement. In particular, this phrase describes a style of development that embraces the use of the CPAN, takes advantage of recent developments in the language, and is rigorous about creating high quality code. While the book "Modern Perl" may be the most visible standard-bearer of this idea, other groups such as the Enlightened Perl Organization have taken up the cause. In late 2012 and 2013, several projects for alternative implementations for Perl 5 started: Perl5 in Perl6 by the Rakudo Perl team, ' by Stevan Little and friends, ' by the Perl11 team under Reini Urban, ' by , and '','' a Kickstarter project led by Will Braswell and affiliated with the Perll11 project.


2020 onwards

In June 2020, Perl 7 was announced as the successor to Perl 5. Perl 7 was to initially be based on Perl 5.32 with a release expected in first half of 2021, and release candidates sooner. This plan was revised in May 2021, without any release timeframe or version of Perl 5 for use as a baseline specified. When Perl 7 is released, Perl 5 will go into long term maintenance. Supported Perl 5 versions however will continue to get important security and bug fixes.


Symbols


Camel

''Programming Perl'', published by
O'Reilly Media O'Reilly Media (formerly O'Reilly & Associates) is an American learning company established by Tim O'Reilly Tim O'Reilly (born 6 June 1954) is the founder of O'Reilly Media O'Reilly Media (formerly O'Reilly & Associates) is an American l ...
, features a picture of a
dromedary camel The dromedary (''Camelus dromedarius'') ( or ), also called the Arabian camel, is a large even-toed ungulate, of the genus '' Camelus'', with one hump on its back. It is the tallest of the three species of camel A camel is an even-toed un ...

dromedary camel
on the cover and is commonly called the "Camel Book". This image has become an unofficial symbol of Perl as well as a general
hacker A hacker is a person skilled in information technology who uses their technical knowledge to achieve a goal or overcome an obstacle, within a computerized system by non-standard means. Though the term ''hacker'' has become associated in popul ...
emblem, appearing on T-shirts and other clothing items. O'Reilly owns the image as a
trademark A trademark (also written trade mark or trade-mark) is a type of intellectual property Intellectual property (IP) is a category of property Property is a system of rights that gives people legal control of valuable things, and also r ...

trademark
but licenses it for
non-commercial A non-commercial (also spelled noncommercial) activity is an activity that does not, in some sense, involve commerce, at least relative to similar activities that do have a commercial objective or emphasis. For example, advertising-free community ...
use, requiring only an acknowledgement and a link to www.perl.com. Licensing for commercial use is decided on a case-by-case basis. O'Reilly also provides "Programming Republic of Perl" logos for non-commercial sites and "Powered by Perl" buttons for any site that uses Perl.


Onion

The Perl Foundation The Perl Foundation (TPF) is a non-profit organization, non-profit, 501(c)(3) organization based in Holland, Michigan. It is dedicated to the advancement of the Perl and Raku (programming language) programming languages through open discussion, co ...
owns an alternative symbol, an onion, which it licenses to its subsidiaries, Perl Mongers,
PerlMonks ''PerlMonks'' is a community website covering all aspects of Perl programming and other related topics such as web applications and system administration. It is often referred to by users as 'The Monastery'. The name PerlMonks, and the general style ...
, Perl.org, and others. The symbol is a
visual pun A visual pun is a pun The pun, also known as paronomasia, is a form of word play Word play or wordplay (also: play-on-words) is a literary technique A narrative technique (known for literary fictional narratives as a literary technique ...
on pearl onion.


Raptor

Sebastian Riedel, the creator of
Mojolicious Mojolicious is a real-time web application framework A web framework (WF) or web application framework (WAF) is a software framework that is designed to support the development of web applications including web services, web resources, and web ...
, created a logo depicting a raptor dinosaur, which is available under a CC-SA License, Version 4.0. The analogue of the raptor comes from a series of talks given by Matt S Trout beginning in 2010.


Overview

According to Wall, Perl has two slogans. The first is " There's more than one way to do it," commonly known as TMTOWTDI. The second slogan is "Easy things should be easy and hard things should be possible".


Features

The overall structure of Perl derives broadly from C. Perl is procedural in nature, with variables,
expressions Expression may refer to: Linguistics * Expression (linguistics), a word, phrase, or sentence * Fixed expression, a form of words with a specific meaning * Idiom, a type of fixed expression * Metaphor#Common types, Metaphorical expression, a parti ...
,
assignment statement In computer programming Computer programming is the process of designing and building an executable computer program to accomplish a specific computing result or to perform a specific task. Programming involves tasks such as: analysis, generat ...
s,
brace Brace(s) or bracing may refer to: Medical * Orthotics, Orthopaedic brace, a device used to restrict or assist body movement ** Back brace, a device limiting motion of the spine *** Milwaukee brace, a kind of back brace used in the treatment of sp ...

brace
-delimited
block Block or blocked may refer to: Arts, entertainment and media Broadcasting * Block programming, the result of a programming strategy in broadcasting * W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 t ...
s,
control structure In computer science, control flow (or flow of control) is the order in which individual Statement (computer science), statements, Instruction (computer science), instructions or function calls of an imperative programming, imperative computer prog ...
s, and
subroutine In computer programming Computer programming is the process of designing and building an executable computer program to accomplish a specific computing result or to perform a particular task. Programming involves tasks such as analysis, generat ...
s. Perl also takes features from shell programming. All variables are marked with leading sigils, which allow variables to be
interpolated In the mathematics, mathematical field of numerical analysis, interpolation is a type of estimation, a method of constructing new data points within the range of a discrete set of known data points. In engineering and science, one often has a nu ...
directly into
strings String or strings may refer to: *String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other objects Arts, entertainment, and media Films * Strings (1991 film), ''Strings'' (1991 fil ...
. However, unlike the shell, Perl uses sigils on all accesses to variables, and unlike most other programming languages that use sigils, the sigil doesn't denote the type of the variable but the type of the expression. So for example, while an array is denoted by the sigil "@" (for example @arrayname), an individual member of the array is denoted by the scalar sigil "$" (for example $arrayname /code>). Perl also has many built-in functions that provide tools often used in shell programming (although many of these tools are implemented by programs external to the shell) such as
sorting Sorting is any process of arranging items systematically, and has two common, yet distinct meanings: # Collating order, ordering: arranging items in a sequence ordered by some criterion; # categorization, categorizing: grouping items with simil ...
, and calling
operating system An operating system (OS) is system software System software is software designed to provide a platform for other software. Examples of system software include operating systems (OS) like macOS, Linux, Android (operating system), Android and Mi ...

operating system
facilities. Perl takes hashes ("associative arrays") from
AWK AWK (''awk'') is a domain-specific language A domain-specific language (DSL) is a computer languageComputer language is a formal language In logic, mathematics, computer science, and linguistics, a formal language consists of string (compute ...
and
regular expression A regular expression (shortened as regex or regexp; also referred to as rational expression) is a sequence of that specifies a ''search ''. Usually such patterns are used by s for "find" or "find and replace" operations on , or for input val ...
s from
sed sed ("stream editor") is a Unix Unix (; trademarked as UNIX) is a family of Computer multitasking, multitasking, multiuser computer operating systems that derive from the original AT&T Corporation, AT&T Unix, whose development started in th ...
. These simplify many parsing, text-handling, and data-management tasks. Shared with
Lisp Lisp (historically LISP) is a family of programming language A programming language is a formal language In logic, mathematics, computer science, and linguistics, a formal language consists of string (computer science), words whose symbo ...
is the implicit return of the last value in a block, and all statements are also expressions which can be used in larger expressions themselves. Perl 5 added features that support complex
data structure In computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its computation as well as practical techniques for their application. Computer science is the study of ...

data structure
s,
first-class function In computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its computation as well as practical techniques for their application. Computer science is the study of Algorit ...
s (that is, closures as values), and an object-oriented programming model. These include
references Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a ''name ...
, packages, class-based Dynamic dispatch, method dispatch, and Scope (programming), lexically scoped variables, along with compiler directives (for example, the strict Directive (programming), pragma). A major additional feature introduced with Perl 5 was the ability to package code as reusable modules. Wall later stated that "The whole intent of Perl 5's module system was to encourage the growth of Perl culture rather than the Perl core." All versions of Perl do automatic Type system, data-typing and automatic memory management. The interpreter knows the type and Computer data storage, storage requirements of every data object in the program; it allocates and frees storage for them as necessary using reference counting (so it cannot deallocate circular dependency, circular data structures without manual intervention). Legal type conversions — for example, conversions from number to string — are done automatically at Run time (program lifecycle phase), run time; illegal type conversions are fatal errors.


Design

The design of Perl can be understood as a response to three broad trends in the computer industry: falling hardware costs, rising labor costs, and improvements in compiler technology. Many earlier computer languages, such as Fortran and C, aimed to make efficient use of expensive computer hardware. In contrast, Perl was designed so that computer programmers could write programs more quickly and easily. Perl has many features that ease the task of the programmer at the expense of greater CPU and memory requirements. These include automatic memory management; dynamic typing; strings, lists, and hashes; regular expressions; type introspection, introspection; and an eval() function. Perl follows the theory of "no built-in limits," an idea similar to the Zero One Infinity rule. Wall was trained as a linguist, and the design of Perl is very much informed by linguistic principles. Examples include Huffman coding (common constructions should be short), good end-weighting (the important information should come first), and a large collection of language primitives. Perl favors language constructs that are concise and natural for humans to write, even where they complicate the Perl interpreter. Perl's Syntax (programming languages), syntax reflects the idea that "things that are different should look different." For example, scalars, arrays, and hashes have different leading sigils. Array indices and hash keys use different kinds of braces. Strings and regular expressions have different standard delimiters. This approach can be contrasted with a language such as
Lisp Lisp (historically LISP) is a family of programming language A programming language is a formal language In logic, mathematics, computer science, and linguistics, a formal language consists of string (computer science), words whose symbo ...
, where the same basic syntax, composed of simple and universal S-expression, symbolic expressions, is used for all purposes. Perl does not enforce any particular programming paradigm (Procedural programming, procedural, Object-oriented programming, object-oriented, Functional programming, functional, or others) or even require the programmer to choose among them. There is a broad practical bent to both the Perl language and the community and culture that surround it. The preface to ''Programming Perl'' begins: "Perl is a language for getting your job done." One consequence of this is that Perl is not a tidy language. It includes many features, tolerates exceptions to its rules, and employs heuristics to resolve syntactical ambiguities. Because of the forgiving nature of the compiler, bugs can sometimes be hard to find. Perl's function documentation remarks on the variant behavior of built-in functions in list and scalar contexts by saying, "In general, they do what you want, unless you want consistency." No written Formal specification, specification or standard for the Perl language exists for Perl versions through Perl 5, and there are no plans to create one for the current version of Perl. There has been only one implementation of the interpreter, and the language has evolved along with it. That interpreter, together with its functional tests, stands as a ''de facto'' specification of the language. Perl 6, however, started with a specification, and several projects aim to implement some or all of the specification.


Applications

Perl has many and varied applications, compounded by the availability of many standard and third-party modules. Perl has chiefly been used to write Common Gateway Interface, CGI scripts: large projects written in Perl include cPanel, Slash (weblog system), Slash, Bugzilla, Request Tracker, RT, TWiki, and Movable Type; high-traffic websites that use Perl extensively include Priceline.com, Craigslist, Internet Movie Database, IMDb, LiveJournal, DuckDuckGo, Slashdot and Ticketmaster. It is also an optional component of the popular LAMP (software bundle), LAMP technology stack for Web development, in lieu of PHP or Python (programming language), Python. Perl is used extensively as a system programming language in the Debian Linux distribution. Perl is often used as a glue language, tying together systems and interfaces that were not specifically designed to interoperate, and for "data munging," that is, converting or processing large amounts of data for tasks such as creating reports. In fact, these strengths are intimately linked. The combination makes Perl a popular all-purpose language for system administrators, particularly because short programs, often called "one-liner programs," can be entered and run on a single Command-line interface, command line. Perl code can be made portable across Microsoft Windows, Windows and Unix; such code is often used by suppliers of software (both Commercial off-the-shelf, COTS and bespoke) to simplify packaging and maintenance of software build- and deployment-scripts. Tk (framework), Perl/Tk and wxPerl are commonly used to add graphical user interfaces to Perl scripts.


Implementation

Perl is implemented as a core interpreter, written in C, together with a large collection of modules, written in Perl and C. , the interpreter is 150,000 lines of C code and compiles to a 1 MB executable on typical machine architectures. Alternatively, the interpreter can be compiled to a link library and embedded in other programs. There are nearly 500 modules in the distribution, comprising 200,000 lines of Perl and an additional 350,000 lines of C code (much of the C code in the modules consists of character encoding tables). The interpreter has an object-oriented architecture. All of the elements of the Perl language—scalars, arrays, hashes, coderefs, file handles—are represented in the interpreter by struct (C programming language), C structs. Operations on these structs are defined by a large collection of Macro (computer science), macros, typedefs, and functions; these constitute the Perl C application programming interface, API. The Perl API can be bewildering to the uninitiated, but its entry points follow a consistent naming scheme, which provides guidance to those who use it. The life of a Perl interpreter divides broadly into a compile phase and a run phase. In Perl, the phases are the major stages in the interpreter's life-cycle. Each interpreter goes through each phase only once, and the phases follow in a fixed sequence. Most of what happens in Perl's compile phase is compilation, and most of what happens in Perl's run phase is execution, but there are significant exceptions. Perl makes important use of its capability to execute Perl code during the compile phase. Perl will also delay compilation into the run phase. The terms that indicate the kind of processing that is actually occurring at any moment are compile time and run time. Perl is in compile time at most points during the compile phase, but compile time may also be entered during the run phase. The compile time for code in a string argument passed to the eval built-in occurs during the run phase. Perl is often in run time during the compile phase and spends most of the run phase in run time. Code in BEGIN blocks executes at run time but in the compile phase. At compile time, the interpreter parses Perl code into a Abstract syntax tree, syntax tree. At run time, it executes the program by Tree traversal, walking the tree. Text is parsed only once, and the syntax tree is subject to optimization before it is executed, so that execution is relatively efficient. Compile-time optimizations on the syntax tree include constant folding and context propagation, but peephole optimization is also performed. Perl has a Turing-complete formal grammar, grammar because parsing can be affected by run-time code executed during the compile phase. Therefore, Perl cannot be parsed by a straight Lex programming tool, Lex/Yacc Lexical analysis, lexer/parser combination. Instead, the interpreter implements its own lexer, which coordinates with a modified GNU bison parser to resolve ambiguities in the language. It is often said that "Only perl can parse Perl," meaning that only the Perl interpreter (''perl'') can parse the Perl language (''Perl''), but even this is not, in general, true. Because the Perl interpreter can simulate a Turing machine during its compile phase, it would need to decide the halting problem in order to complete parsing in every case. It is a longstanding result that the halting problem is undecidable, and therefore not even perl can always parse Perl. Perl makes the unusual choice of giving the user access to its full programming power in its own compile phase. The cost in terms of theoretical purity is high, but practical inconvenience seems to be rare. Other programs that undertake to parse Perl, such as Static program analysis, source-code analyzers and Indent style, auto-indenters, have to contend not only with ambiguous Language construct, syntactic constructs but also with the Recursive language, undecidability of Perl parsing in the general case. Adam Kennedy (programmer), Adam Kennedy's PPI project focused on parsing Perl code as a document (retaining its integrity as a document), instead of parsing Perl as executable code (that not even Perl itself can always do). It was Kennedy who first conjectured that "parsing Perl suffers from the 'halting problem'," which was later proved. Perl is distributed with over 250,000 Functional testing, functional tests for core Perl language and over 250,000 functional tests for core modules. These run as part of the normal build process and extensively exercise the interpreter and its core modules. Perl developers rely on the functional tests to ensure that changes to the interpreter do not introduce software bugs; additionally, Perl users who see that the interpreter passes its functional tests on their system can have a high degree of confidence that it is working properly.


Availability

Perl is dual licensed under both the Artistic License 1.0 and the GNU General Public License. Distributions are available for most
operating system An operating system (OS) is system software System software is software designed to provide a platform for other software. Examples of system software include operating systems (OS) like macOS, Linux, Android (operating system), Android and Mi ...

operating system
s. It is particularly prevalent on
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser Multi-user software is computer software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to ...

Unix
and Unix-like systems, but it has been ported to most modern (and many obsolete) platforms. With only six reported exceptions, Perl can be compiled from source code on all POSIX-compliant, or otherwise-Unix-compatible, platforms. Because of unusual changes required for the classic Mac OS environment, a special port called MacPerl was shipped independently. The Comprehensive Perl Archive Network carries a complete list of supported platforms with links to the distributions available on each. CPAN is also the source for publicly available Perl modules that are not part of the core Perl distribution.


Windows

Users of
Microsoft Windows Microsoft Windows, commonly referred to as Windows, is a group of several families, all of which are developed and marketed by . Each family caters to a certain sector of the computing industry. Active Microsoft Windows families include an ...
typically install one of the native binary distributions of Perl for Win32, most commonly Strawberry Perl or ActivePerl. Compiling Perl from source code under Windows is possible, but most installations lack the requisite C compiler and build tools. This also makes it difficult to install modules from the CPAN, particularly those that are partially written in C. ActivePerl is a closed-source distribution from ActiveState that has regular releases that track the core Perl releases. The distribution previously included the Perl package manager (PPM), a popular tool for installing, removing, upgrading, and managing the use of common Perl modules; however, this tool was discontinued as of ActivePerl 5.28. Included also is PerlScript, a Windows Script Host (WSH) engine implementing the Perl language. Visual Perl is an ActiveState tool that adds Perl to the Visual Studio .NET development suite. A VBScript-to-Perl converter, as well as a Perl compiler for Windows, and converters of awk and
sed sed ("stream editor") is a Unix Unix (; trademarked as UNIX) is a family of Computer multitasking, multitasking, multiuser computer operating systems that derive from the original AT&T Corporation, AT&T Unix, whose development started in th ...
to Perl have also been produced by this company and included on the ''ActiveState CD for Windows'', which includes all of their distributions plus the Komodo IDE and all but the first on the Unix/Linux/Posix variant thereof in 2002 and subsequently. Strawberry Perl is an open-source distribution for Windows. It has had regular, quarterly releases since January 2008, including new modules as feedback and requests come in. Strawberry Perl aims to be able to install modules like standard Perl distributions on other platforms, including compiling XS modules. The Cygwin emulation layer is another way of running Perl under Windows. Cygwin provides a Unix-like environment on Windows, and both Perl and CPAN are available as standard pre-compiled packages in the Cygwin setup program. Since Cygwin also includes GNU Compiler Collection, gcc, compiling Perl from source is also possible. A perl executable is included in several Windows Resource kits in the directory with other scripting tools. Implementations of Perl come with the MKS Toolkit, Interix (the base of earlier implementations of Windows Services for Unix), and UWIN.


Database interfaces

Perl's text-handling capabilities can be used for generating SQL queries; arrays, hashes, and automatic memory management make it easy to collect and process the returned data. For example, in Tim Bunce's Perl DBI application programming interface (API), the arguments to the API can be the text of SQL queries; thus it is possible to program in multiple languages at the same time (e.g., for generating a Web page using HTML, JavaScript, and SQL in a here document). The use of Perl variable interpolation to programmatically customize each of the SQL queries, and the specification of Perl arrays or hashes as the structures to programmatically hold the resulting data sets from each SQL query, allows a high-level mechanism for handling large amounts of data for post-processing by a Perl subprogram. 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 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 American National Standards Institute, ANSI SQL databases. DBI provides caching for database handles and queries, which can greatly improve performance in long-lived execution environments such as mod perl, helping high-volume systems avert load spikes as in the Slashdot effect. In modern Perl applications, especially those written using web frameworks such as Catalyst (software), Catalyst, the DBI module is often used indirectly via object-relational mappers such as DBIx::Class, Class::DBI or Rose::DB::Object that generate SQL queries and handle data transparently to the application author.


Comparative performance

The Computer Language Benchmarks Game compares the performance of implementations of typical programming problems in several programming languages. The submitted Perl implementations typically perform toward the high end of the memory-usage spectrum and give varied speed results. Perl's performance in the benchmarks game is typical for interpreted languages. Large Perl programs start more slowly than similar programs in compiled languages because perl has to compile the source every time it runs. In a talk at the Yet Another Perl Conference, YAPC::Europe 2005 conference and subsequent article "A Timely Start," Jean-Louis Leroy found that his Perl programs took much longer to run than expected because the perl interpreter spent significant time finding modules within 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 benchmarks that measure very short execution times are likely to be skewed due to this overhead. A number of tools have been introduced to improve this situation. The first such tool was Apache's mod perl, which sought to address one of the most-common reasons that small Perl programs were invoked rapidly: Common Gateway Interface, CGI World Wide Web, Web development. ActiveState, ActivePerl, via Microsoft ISAPI, 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

The most critical routines can be written in other languages (such as C), which can be connected to Perl via simple Inline modules or the more complex, but flexible, XS (Perl), XS mechanism.


Perl 5

Perl 5, the language usually referred to as "Perl", continues to be actively developed. Perl 5.12.0 was released in April 2010 with some new features influenced by the design of Perl 6, followed by Perl 5.14.1 (released on June 17, 2011), Perl 5.16.1 (released on August 9, 2012.), and Perl 5.18.0 (released on May 18, 2013). Perl 5 development versions are released on a monthly basis, with major releases coming out once per year. The relative proportion of Internet searches for "Perl programming", as compared with similar searches for other programming languages, steadily declined from about 10% in 2005 to about 2% in 2011, to about 0.7% in 2020.


Raku (Perl 6)

At the 2000 O'Reilly Open Source Convention, Perl Conference, 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, which submitted more than 300 Request for Comments, RFCs. Wall spent the next few years digesting the RFCs and synthesizing them into a coherent framework for Perl 6. He presented his design for Perl 6 in a series of documents called "apocalypses"numbered to correspond to chapters in ''Programming Perl''. , the developing specification of Perl 6 was encapsulated in design documents called Synopsesnumbered to correspond to Apocalypses. Thesis work by Bradley M. Kuhn, overseen by Wall, considered the possible use of the Java virtual machine as a runtime for Perl. Kuhn's thesis showed this approach to be problematic. In 2001, it was decided that Perl 6 would run on a cross-language virtual machine called
Parrot Parrots, also known as psittacines , are bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class ...
. This will mean that other languages targeting the Parrot will gain native access to CPAN, allowing some level of cross-language development. In 2005,
Audrey Tang Audrey Tang ( zh, t=唐鳳, p=Táng Fèng; born 18 April 1981) is a Taiwanese free software Free software (or libre software) is computer software Software is a collection of Instruction (computer science), instructions and data (compu ...

Audrey Tang
created the Pugs project, an implementation of Perl 6 in Haskell. This acted as, 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 Libera Chat #raku IRC channel. Many functional programming influences were absorbed by the Perl 6 design team. In 2012, Perl 6 development was centered primarily on two compilers: # Rakudo, an implementation running on the Parrot virtual machine and the Java virtual machine. # Niecza, which targets the Common Language Runtime. In 2013, MoarVM (“Metamodel On A Runtime”), a C language-based virtual machine designed primarily for Rakudo was announced. In October 2019, Perl 6 was renamed to Raku. only the Rakudo implementation and MoarVM are under active development, and other virtual machines, such as the Java Virtual Machine and JavaScript, are supported.


Perl 7

Perl 7 was announced on 24 June 2020 at "The Perl Conference in the Cloud" as the successor to Perl 5. Based on Perl 5.32, Perl 7 is designed to be Backward_compatibility, backwards compatible with modern Perl 5 code; Perl 5 code, without Boilerplate code, boilerplate (pragma) header needs adding use compat::perl5; to stay compatible, but modern code can drop some of the boilerplate.


Perl community

Perl's culture and community has developed alongside the language itself. Usenet 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 Wall's first "State of the Onion" talk.


State of the Onion

State of the Onion is the name for Wall's yearly keynote-style summaries on the progress of Perl and its community. They are characterized by his hallmark humor, employing references to Perl's culture, the wider hacker culture, Wall's linguistic background, sometimes his family life, and occasionally even his Christian background. Each talk is first given at various Perl conferences and is eventually also published online.


Perl pastimes


JAPHs

In email, Usenet, and message board postings, "Just another Perl hacker" (JAPH) programs are a common trend, originated by Randal L. Schwartz, one of the earliest professional Perl trainers. In the parlance of Perl culture, Perl programmers are known as Perl hackers, and from this derives the practice of writing short programs to print out the phrase "Just another Perl hacker". In the spirit of the original concept, these programs are moderately obfuscated and short enough to fit into the signature of an email or Usenet message. The "canonical" JAPH as developed by Schwartz includes the comma at the end, although this is often omitted.


Perl golf

Perl "golf" is the pastime of reducing the number of characters (key "strokes") used in a Perl program to the bare minimum, much in the same way that golf players seek to take as few shots as possible in a round. The phrase's first use emphasized the difference between pedestrian code meant to teach a newcomer and terse hacks likely to amuse experienced Perl programmers, an example of the latter being JAPHs that were already used in signatures in Usenet postings and elsewhere. Similar stunts had been an unnamed pastime in the language APL (programming language), APL in previous decades. The use of Perl to write a program that performed RSA (algorithm), RSA encryption prompted a widespread and practical interest in this pastime. In subsequent years, the term "code golf" has been applied to the pastime in other languages. A Perl Golf Apocalypse was held at Perl Conference 4.0 in Monterey, California in July 2000.


Obfuscation

As with C, obfuscated code competitions were a well known pastime in the late 1990s. The Obfuscated Perl Contest was a competition held by The Perl Journal from 1996 to 2000 that made an arch virtue of Perl's syntactic flexibility. Awards were given for categories such as "most powerful"—programs that made efficient use of space—and "best four-line signature" for programs that fit into four lines of 76 characters in the style of a Usenet signature block.


Poetry

Perl poetry is the practice of writing poems that can be compiled as legal Perl code, for example the piece known as Black Perl. Perl poetry is made possible by the large number of English words that are used in the Perl language. New poems are regularly submitted to the community at
PerlMonks ''PerlMonks'' is a community website covering all aspects of Perl programming and other related topics such as web applications and system administration. It is often referred to by users as 'The Monastery'. The name PerlMonks, and the general style ...
.


Perl on IRC

There are a number of Internet Relay Chat, IRC channels that offer support for the language and some modules.


CPAN Acme

There are also many examples of code written purely for entertainment on the CPAN. Lingua::Romana::Perligata, for example, allows writing programs in Latin. Upon execution of such a program, the module translates its source code into regular Perl and runs it. The Perl community has set aside the "Acme Corporation, Acme" namespace for modules that are fun in nature (but its scope has widened to include exploratory or experimental code or any other module that is not meant to ever be used in production). Some of the Acme modules are deliberately implemented in amusing ways. This includes Acme::Bleach, one of the first modules in the Acme:: namespace, which allows the program's source code to be "whitened" (i.e., all characters replaced with whitespace) and yet still work.


Example code

In older versions of Perl, one would write the Hello World program as: print "Hello, World!\n"; Here is a more complex Perl program, that counts down seconds from a given starting value: #!/usr/bin/perl use strict; use warnings; my ( $remaining, $total ); $remaining = $total = shift(@ARGV); STDOUT->autoflush(1); while ( $remaining ) print "\n"; The perl interpreter can also be used for one-off scripts on the command line. The following example (as invoked from an sh-compatible shell, such as Bash) translates the string "Bob" in all files ending with .txt in the current directory to "Robert": $ perl -i.bak -lp -e 's/Bob/Robert/g' *.txt


Criticism

Perl has been referred to as "wikt:line noise, line noise" and a write-only language by its critics. The earliest such mention was in the first edition of the book ''Learning Perl'', a Perl 4 tutorial book written by Randal L. Schwartz, in the first chapter of which he states: "Yes, sometimes Perl looks like line noise to the uninitiated, but to the seasoned Perl programmer, it looks like checksummed line noise with a mission in life." He also stated that the accusation that Perl is a write-only language could be avoided by coding with "proper care". The Perl overview document ' states that the names of built-in "magic" scalar Variable (computer science), variables "look like punctuation or line noise". However, the English module provides both long and short English alternatives. ' document states that line noise in regular expressions could be mitigated using the /x modifier to add whitespace. According to the ''Perl 6 FAQ'', Perl 6 was designed to mitigate "the usual suspects" that elicit the "line noise" claim from Perl 5 critics, including the removal of "the majority of the punctuation variables" and the sanitization of the regex syntax. The ''Perl 6 FAQ'' also states that what is sometimes referred to as Perl's line noise is "the actual syntax of the language" just as gerunds and Preposition and postposition, prepositions are a part of the English language. In a December 2012 blog posting, despite claiming that "Rakudo Perl 6 has failed and will continue to fail unless it gets some adult supervision", chromatic (programmer), chromatic stated that the design of Perl 6 has a "well-defined grammar" as well as an "improved type system, a unified object system with an intelligent metamodel, metaoperators, and a clearer system of context that provides for such niceties as pervasive laziness". He also stated that "Perl 6 has a coherence and a consistency that Perl 5 lacks."


See also

* Outline of Perl * Perl Data Language * Perl Object Environment * Plain Old Documentation


References


Further reading


Learning Perl
6th Edition (2011), O'Reilly. Beginner-level introduction to Perl.

1st Edition (2012), Wrox. A beginner's tutorial for those new to programming or just new to Perl.
Modern Perl
2nd Edition (2012), Onyx Neon. Describes Modern Perl programming techniques.
Programming Perl
4th Edition (2012), O'Reilly. The definitive Perl reference.
Effective Perl Programming
2nd Edition (2010), Addison-Wesley. Intermediate- to advanced-level guide to writing idiomatic Perl. * ''Perl Cookbook'', . Practical Perl programming examples. * Functional programming techniques in Perl.


External links

* {{Authority control Perl, American inventions Programming languages C programming language family Cross-platform software Dynamic programming languages Dynamically typed programming languages Free compilers and interpreters Free software programmed in C High-level programming languages Multi-paradigm programming languages Object-oriented programming languages Procedural programming languages Programming languages created in 1987 Scripting languages Software using the Artistic license Text-oriented programming languages Unix programming tools Articles with example Perl code