Book Image

Perl 6 Deep Dive

By : Andrew Shitov
Book Image

Perl 6 Deep Dive

By: Andrew Shitov

Overview of this book

Perl is a family of high-level, general-purpose, interpreted, dynamic programming languages consisting of Perl 5 and Perl 6. Perl 6 helps developers write concise and declarative code that is easy to maintain. This book is an end-to-end guide that will help non-Perl developers get to grips with the language and use it to solve real-world problems. Beginning with a brief introduction to Perl 6, the first module in the book will teach you how to write and execute basic programs. The second module delves into language constructs, where you will learn about the built-in data types, variables, operators, modules, subroutines, and so on available in Perl 6. Here the book also delves deeply into data manipulation (for example, strings and text files) and you will learn how to create safe and correct Perl 6 modules. You will learn to create software in Perl by following the Object Oriented Paradigm. The final module explains in detail the incredible concurrency support provided by Perl 6. Here you will also learn about regexes, functional programming, and reactive programming in Perl 6. By the end of the book, with the help of a number of examples that you can follow and immediately run, modify, and use in practice, you will be fully conversant with the benefits of Perl 6.
Table of Contents (15 chapters)

Writing our Hello World program

So far, as we have installed the Rakudo Star compiler, it's now time to create the first program in Perl 6. It will print Hello, World! and exit.

The program is really easy. All you need is a single line with the only instruction to call the built-in say function. It takes the string, prints it to the console, and adds a new line after it.

This is how the whole program looks:

say 'Hello, World!'

Save the code to the file, say, hello.pl, and pass it to the compiler as follows:

$ perl6 hello.pl

It will compile the program and immediately execute it. The result is the desired string on the screen:

Hello, World!

Notice that the output ends with a new line. This is the behavior of the built-in say function. Alternatively, we could use another method of printing the output, using the print built-in function. Unlike say, it will not add the new line at the end of the output, so you have to do it yourself by adding the special symbol \n:

print "Hello, World!\n"

Notice that this time, a pair of double quotes is used. Double quotes treat special characters such as \n differently compared to single quotes. Inside double quotes, the \n converts to a new line character. That will not happen in single quotes, and, in that case, \n will appear on the screen as a sequence of two characters, and \n.

Because the program contains only one line of code, it is not necessary to end it with a semicolon. However, you can always do that:

say "Hello, World!";

This program produces exactly the same output as before.