What is Perl?

by Stephen M. Walker II, Co-Founder / CEO

What is Perl?

Perl is a high-level, general-purpose, interpreted programming language that was developed by Larry Wall in 1987. It was originally designed for text manipulation but has since evolved to be used for a wide range of tasks including system administration, web development, network programming, and more.

Perl is known for its expressiveness and flexibility, allowing developers to write concise and highly compressible code. It borrows features from several other languages such as C, awk, sed, sh, and BASIC, among others. This includes variables, expressions, statements, control structures, and subroutines from C, and data type identification and inbuilt functions often used in shell programming.

Perl supports both procedural and object-oriented programming. It also includes auto data typing and memory management, with the interpreter understanding storage and memory requirements for each data type, allocating and deallocating memory based on usage.

Perl has a large and active worldwide community, with over 230 local groups, mailing lists, and support/discussion websites. The Comprehensive Perl Archive Network (CPAN) provides over 25,000 open-source distributions available for download.

Perl is also known for its powerful regular expression handling, making it ideal for text processing and data manipulation tasks. It works with HTML, XML, and other markup languages, and supports Unicode.

Perl is an open-source software, licensed under its Artistic License, or the GNU General Public License (GPL). It's worth noting that Perl 6, now known as Raku, is a sister language to Perl, part of the Perl family, but not intended as a replacement for Perl.

Design and features of Perl

Perl is a high-level, general-purpose, interpreted, dynamic programming language that has been in development for over 36 years. It is open-source and free to contribute to, with a large and active community of developers. Perl is known for its "There's more than one way to do it" philosophy, which encourages developers to solve problems using their preferred methods.

Perl is procedural in nature, with variables, expressions, assignment statements, brace-delimited blocks, control structures, and subroutines. It also supports object-oriented, procedural, and functional programming. Perl borrows syntax and features from other languages such as C, awk, sed, sh, and BASIC. All variables in Perl are marked with leading sigils, which allow variables to be interpolated directly into strings.

Perl's primary strength is in text processing, making it ideal for tasks such as parsing log files, generating SQL queries, and working with HTML, XML, and other markup languages. It also has powerful utilities for text manipulation. Perl's database integration interface (DBI) supports third-party databases including Oracle, Sybase, Postgres, MySQL, and many others. It can interface with external C/C++ libraries through XS or SWIG.

Perl can be embedded into web servers to speed up processing and into other systems such as database servers. It has over 25,000 open-source modules available from the Comprehensive Perl Archive Network (CPAN), providing many powerful extensions. Perl also includes a specialized syntax for writing regular expressions, and the interpreter contains an engine for matching strings to these expressions.

Perl programs consist of a sequence of declarations and statements, which run from the top to the bottom. Control structures like loops and subroutines allow you to jump around within the code. Perl is a free-form language, meaning you can format and indent it however you like. Whitespace serves mostly to separate tokens.

Perl is suitable for a wide range of applications, including web development, GUI development, and CGI scripts. It is also used for system administration tasks and enhancing shell scripts. It is often referred to as the "Swiss Army chainsaw" of the internet due to its versatility and efficiency.

What are the advantages of using Perl over other programming languages?

Perl offers several advantages over other programming languages, which can be particularly beneficial depending on the specific use case:

  1. Text Processing: Perl's powerful regular expression engine and string manipulation capabilities make it a strong choice for text processing tasks.

  2. Unix Integration: Perl is very Unix-friendly, making it an excellent choice for scripting and automating tasks on Unix-based systems.

  3. Flexibility: Perl allows for multiple programming paradigms, including procedural and object-oriented programming, and it doesn't force a particular style, giving developers the freedom to solve problems in various ways.

  4. CPAN: The Comprehensive Perl Archive Network (CPAN) is a vast repository of Perl modules that can be easily integrated into Perl applications, providing a wealth of pre-written code to speed up development.

  5. Database Integration: Perl has strong support for database integration, making it easy to interact with various databases.

  6. Portability: Perl code is generally portable across different operating systems, which can reduce development costs and complexity.

  7. Glue Language: Perl is often referred to as a "glue" language because it is good at integrating with other languages and technologies, which can be useful in complex environments where different systems need to work together.

  8. Mature: Perl has been around for a long time, which means it has a mature ecosystem and a wealth of documentation and community support.

  9. Open Source: Perl is open-source, which means it is free to use, modify, and distribute, and it benefits from contributions from a global community of developers.

While Perl has these advantages, it's important to note that it may not be the best choice for all scenarios. For example, Perl's flexibility can lead to code that is difficult to read and maintain, especially for those new to the language. Additionally, Perl is an interpreted language, which can be slower than compiled languages for certain types of tasks. However, for tasks involving complex text processing, system administration, and rapid prototyping, Perl's advantages can be quite significant.

Perl syntax and code examples

Perl is a high-level, general-purpose, interpreted, dynamic programming language. It was originally developed for text processing but has since evolved to handle a wide range of tasks including system administration, web development, network programming, and more. Perl is known for its flexibility and power, especially in text and file manipulation.

Basic Syntax

A Perl program consists of a sequence of declarations and statements, which run from the top to the bottom. Control structures like loops and subroutines allow you to jump around within the code. Every simple statement must end with a semicolon (;). Perl is a free-form language, meaning you can format and indent it however you like. Whitespace serves mostly to separate tokens.

Variables

Variables in Perl are used to store data. They are user-defined words that hold the values passed to the program. Every Perl program contains values on which the code performs its operations. These values can’t be manipulated or stored without the use of a variable.

There are three types of variables in Perl:

  • Scalars: A scalar is a single unit of data. It can be a number, a string, or a reference. It is represented by a dollar sign ($).
  • Arrays: An array is an ordered collection of scalars. It is represented by an at sign (@).
  • Hashes: A hash is a set of key/value pairs. It is represented by a percent sign (%) and is also known as an associative array.

Control Structures

Perl provides several control structures including conditional statements and loops. The if statement is used for conditional execution of code. Loops in Perl include for, foreach, while, and until.

Subroutines

Subroutines in Perl are user-defined functions that can be called to perform a specific task. They help in reducing the complexity of the code.

Regular Expressions

Perl includes a specialized syntax for writing regular expressions, and the interpreter contains an engine for matching strings to these expressions.

File Handling

Perl is particularly efficient in file parsing and handling. File operations in Perl are performed using a FILEHANDLE, which is defined when opening a file for either read or write.

Code Examples

Here are some basic Perl code examples:

  1. Hello World Program
print "Hello, World!\n";
  1. Variable Declaration and Usage
my $name = "John Doe";
print "Hello, $name\n";
  1. Array and Hash Declaration and Usage
my @fruits = ("apple", "banana", "cherry");
print "First fruit: $fruits\n";

my %fruit_color = ("apple" => "red", "banana" => "yellow", "cherry" => "red");
print "The color of an apple is $fruit_color{'apple'}\n";
  1. Conditional Statements and Loops
my $age = 20;
if ($age > 18) {
    print "You are an adult\n";
}

for my $i (0..5) {
    print "$i\n";
}
  1. Subroutine
sub greet {
    my $name = shift;
    print "Hello, $name\n";
}

greet("John Doe");
  1. File Handling
open my $file, '<', 'input.txt' or die "Can't open file: $!";
while (my $line = <$file>) {
    print $line;
}
close $file;

Remember, Perl is a very flexible language and there are often many ways to accomplish the same task. The examples provided here are just a starting point and there's a lot more to explore and learn in Perl.

Pros and cons of using Perl

Perl, a high-level, general-purpose, interpreted programming language, has several advantages and disadvantages that can influence its use in different scenarios.

Advantages of Perl

  1. Text Processing: Perl is highly efficient in text and string manipulation tasks, making it a preferred language for developers working with large volumes of text data.

  2. Unix Integration: Perl is very Unix-friendly, excelling at tasks like pipes, file slurping, and inter-process communication.

  3. Flexibility: Perl allows for multiple programming paradigms, including procedural and object-oriented programming, and it doesn't enforce a particular style, giving developers the freedom to solve problems in various ways.

  4. CPAN: The Comprehensive Perl Archive Network (CPAN) is a vast repository of Perl modules that can be easily integrated into Perl applications, providing a wealth of pre-written code to speed up development.

  5. Database Integration: Perl has strong support for database integration, making it easy to interact with various databases.

  6. Portability: Perl code is generally portable across different operating systems, which can reduce development costs and complexity.

  7. Glue Language: Perl is often referred to as a "glue" language because it is good at integrating with other languages and technologies, which can be useful in complex environments where different systems need to work together.

  8. Mature: Perl has been around for a long time, which means it has a mature ecosystem and a wealth of documentation and community support.

  9. Open Source: Perl is open-source, which means it is free to use, modify, and distribute, and it benefits from contributions from a global community of developers.

Disadvantages of Perl

  1. Readability: Perl's flexibility can lead to code that is difficult to read and maintain, especially for those new to the language.

  2. Performance: As an interpreted language, Perl can be slower than compiled languages for certain types of tasks.

  3. Portability Issues with CPAN Modules: A Perl program containing CPAN modules may not run on another system which doesn't have CPAN modules installed.

  4. Legacy Code: There is a lot of legacy code written in earlier versions of the language that may not be compatible with newer versions.

  5. Security Concerns: Perl has some security concerns, such as the possibility of code injection attacks if the input data is not properly sanitized.

  6. Large Codebase Issues: Perl starts creating problems when the code is larger than 200 lines, making it difficult to maintain over time.

Despite these disadvantages, Perl remains a powerful tool for certain tasks, particularly those involving complex text processing, system administration, and rapid prototyping. The choice to use Perl should be informed by the specific requirements of the project and the capabilities of the development team.

Perl vs. Python

Perl and Python are both high-level, interpreted programming languages that have been around since the 1970s and are used for automation, scripting, and web development. However, they have significant differences in syntax, use cases, community support, and popularity.

Syntax Perl's syntax is similar to C, which can be cryptic for beginners due to its use of special characters and symbols. Code blocks in Perl are marked and identified using braces, and whitespaces do not hold significance. Perl uses a semicolon (;) to end a code line. On the other hand, Python uses a syntax that is clean, simple, and focuses on readability. Code blocks are marked and identified by the use of indentation, and whitespaces hold significance and can cause syntax errors. Semicolons (;) are not required at the end of each code line in Python.

Use Cases Perl was originally developed for text processing, such as extracting required information from a specified text file and converting the text file into a different format. It is primarily used for creating Common Gateway Interface (CGI) scripts in projects like Bugzilla and as a system programming language in Debian. It is also used as a scripting language for processing large volumes of data for tasks such as report generation and file scanning. Python, however, is widely used in web development, machine learning, desktop applications, data science, and data analysis. It is the top choice, alongside R, for data scientists and data analysts.

Community Support Both Perl and Python have active and large developer communities. However, Python's community is larger and has more online resources. Python also has a larger body of development kits, code snippets, frameworks, and platforms due to its larger community.

Popularity Python is more popular than Perl in terms of job opportunities and usage. According to the TIOBE index, Python is the third-most-popular programming language, while Perl is ranked 18th. Python's popularity has been growing, especially in the fields of web development and machine learning, while Perl's popularity has seen a significant decline.

Performance In specific scenarios, Perl's streamlined syntax may give it a speed advantage, especially in text processing and report generation where it can perform up to 20 times faster than Python for certain text manipulation actions. However, Python's scalability is generally more favorable due to its versatility and extensive ecosystem, making it a more popular choice for a wide range of application sizes and complexities.

The choice between Perl and Python depends on the specific needs of your project and your personal preference. For projects requiring quick scripting and text manipulation, Perl's expressive syntax might be beneficial. However, for projects where code maintainability and readability are important, Python's simplicity and versatility make it a more suitable choice.

History and future of Perl

Perl is a high-level, general-purpose programming language that was created by Larry Wall in 1987. It was originally designed for text processing but has since evolved to become a full-featured programming language used widely in web system administration, network programming, and more. Perl 5.000, released on October 17, 1994, was a nearly complete rewrite of the interpreter, adding many new features to the language, including objects, references, lexical (my) variables, and modules.

Perl was a favorite among web developers in the late 20th and early 21st centuries for its flexible, continually evolving text-processing and problem-solving capabilities. It has a vibrant development community in CPAN, with a vast archive of Perl modules. Perl's database integration interface (DBI) supports third-party databases including Oracle, Sybase, Postgres, MySQL, and many others. Perl interfaces with external C/C++ libraries through XS or SWIG.

Perl has been under heavy development, with Perl 7 being the current focus. There's also a discussion about the future needs for Perl 8. As of January 10, 2024, the current stable version of Perl is 5.38.2. Perl is actively maintained and developed by a large group of dedicated volunteers, and it's expected to be developed and maintained for many years to come.

The Raku project, formerly known as Perl 6, is a separate language that has its own development team. It's not intended as a replacement for Perl, but as its own thing, and libraries exist to allow you to call Perl code from Raku programs and vice versa.

Perl's future seems promising due to its continuous evolution, taking inspiration from other languages, and providing production-ready implementations for event loops, promises, and object-oriented programming. In recent years, the Corinna specifications and Object::Pad implementation are preparing the introduction of modern features.

It's worth noting that while Perl continues to be used and developed, its popularity has been overshadowed by other languages like Python and JavaScript. Despite this, Perl remains relevant due to its powerful text processing and data manipulation capabilities, making it a valuable tool for specific tasks and legacy systems.

More terms

What is Amazon Bedrock?

Amazon Bedrock is a fully managed service that offers a choice of high-performing foundation models from leading AI companies like AI21 Labs, Anthropic, Cohere, and Stability AI, along with a broad set of capabilities for building generative AI applications with security, privacy, and responsible AI.

Read more

What is an issue tree?

An issue tree is a graphical representation of a problem or question, broken down into its component parts or causes. It helps organize complex issues by breaking them down into smaller, more manageable components, making it easier to analyze and address each part individually.

Read more

It's time to build

Collaborate with your team on reliable Generative AI features.
Want expert guidance? Book a 1:1 onboarding session from your dashboard.

Start for free