NAME

Perl::Tutorial::HelloWorld - Hello World for Perl

SYNOPSIS

  #!/usr/bin/perl
  #
  # The traditional first program.

  # Strict and warnings are recommended.
  use strict;
  use warnings;

  # Print a message.
  print "Hello, World!\n";

DESCRIPTION

Running the program

Open a text editor, and type in the above program. Save it in a file named "hello". Then open a terminal window.

First ensure the file is given executable permissions:

  chmod u+x hello

Then you can run the program using either of the following:

  ./hello
  perl hello

You should see it print "Hello, World!" to the console.

The first line

Every Perl program should start with a line similar to one of these:

  #!/usr/bin/perl
  #!/usr/bin/env perl

or on Windows:

  #!C:\Perl\bin\perl.exe
  #!C:\strawberry\perl\bin\perl.exe

The first line is known as the "shebang line", and is used by UNIX-like systems to look up the path to the Perl interpreter.

Comments

Comments in Perl always start with a '#' character:

  # This is a single-line comment.

  # This comment extends over two lines
  # to illustrate multi-line comments.

  print 'hello'; # And here is an inline comment.

Anything to the right of a '#' will be ignored.

Statements

Statements always end with a semicolon in Perl:

  print 'hello';

  print 'This statement extends over two lines
  because there is no semicolon on the first line.';

It is possible to have more than one statement on a single line, but generally this would not be very readable.

Strict and Warnings

These two statements turn on the 'strict' and 'warnings' pragmas:

  use strict;
  use warnings;

These are strongly encouraged for all Perl programs - they tell the Perl interpreter to check for programming errors like undeclared variables.

Printing to standard output

To print some output to the terminal, you can use the 'print' function:

  print "Hello, World!\n";

In this case, the double-quoted string "Hello, World!\n" is being printed. You should see that the "\n" sequence does not appear on the console - it is used to mark the end of a line. Double-quoted strings can contain various other escape sequences.

SEE ALSO

Perl::Tutorial

COPYRIGHT AND LICENSING

Copyright (C) 2011 Copperly Ltd.

This documentation is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Perl::Tutorial

perl -MCPAN -e shell
install Perl::Tutorial