PERL/C2/Comments-in-Perl/English

Title of script: Comments in Perl

Author: Amol

Keywords: Comments in Perl, Video Tutorials, Scalars in Perl

Visual Cue	Narration
Slide	Welcome to the spoken tutorial on Comments in Perl.
Slide:Learning Objectives	In this tutorial, we will learn about Comments in Perl
Slide:System Requirements	I am using Ubuntu Linux12.04 operating system and Perl 5.14.2 that is, Perl revision 5 version 14 and subversion 2 I will also be using the gedit Text Editor. You can use any text editor of your choice. You should have Basic knowledge of Compiling, Executing and Variables in Perl If not, please go through the relevant spoken tutorials on the spoken tutorial website
Slide	Commenting a piece of code in Perl can be done in two ways: a. Single Line b. Multi Line
Slide	Single Line This type of comment is used when user wants to comment a single line of code or to add one liner text to explain the functionality of a piece of code This type of comment starts with the symbol # (hash).
	Here is a demo. Let us open a new file in the Text Editor.
Switch to the Terminal and type gedit singlemulti.pl & and press Enter.	Open the Terminal and type - gedit comments dot pl &
Highlight &	Once again, reminding you that the ampersand is used to free the command prompt in the terminal. And press enter
Type # Declaring count variable $count = 1; print “Count is $count \n”; # prints Count is 1	Now type the following commands. hash Declaring count variable press enter dollar count space equal to space 1 semicolon press enter print space double quotes Count is dollar count slash n double quote complete semicolon space hash prints Count is 1
Save the file.	Now Save this file by pressing ctlr s file and execute the Perl script.
Switch to the Terminal and type perl -c singlemulti.pl and press Enter	Switch to the Terminal, and type perl hyphen c comments dot pl and press Enter. This tells us that there is no syntax error
Then type perl singlemulti.pl and press Enter	Now type perl comments dot pl and press Enter.
Point to the output	It will show the following output - Count is 1
Go to gedit and type #!/usr/bin/perl	Let us switch back to gedit. in gedit, go to the first line and press enter. Go back to the first line and type the following code. Hash exclamation mark slash usr slash bin slash perl
Slide	This line in Perl is called as a shebang line and is the first line in a Perl program. It tells where to find the Perl Interpreter.
Slide	Note: Though this line starts with hash symbol, it will not be considered as a single line comment by Perl. Now let us look at multiline comments
Slide	Multi Line This type of comment is used when user wants to comment a piece of code or to add description/usage of piece of code This type of comment starts with the symbol equal to head and ends with equal to cut
Type =head print “ count variable will be used for counting purpose” =cut above $count = 1;	Lets switch back to gedit and type the following - in the comments dot pl file at the end of file type equal to head press enter print space double quote count variable will be used for counting purpose double quote complete press enter equal to cut
Save the file and close it.	Save the file, close it and execute the Perl script.
Switch to the Terminal and type perl -c singlemulti.pl and press Enter.	On the Terminal, type perl hyphen c comments dot pl and press Enter. No syntax error
Then type perl singlemulti.pl and press Enter	so let us execute it perl comments dot pl and press Enter.
Point to the output	It will show the same output as before. Count is 1
Switch back to gedit Point to the sentence “count variable will be used for counting purpose”	It does not print the sentence “count variable will be used for counting purpose”
Point to =head and =cut	This is because we commented the portion using equal to head and equal to cut
Slide	You can either use =head =cut or =begin =end. These are not the special keywords used by Perl.
	Please note there should not be any leading or trailing space(s) before = to sign and after the head, cut, begin or end word.
Switch to the Terminal	Open the Terminal once again.
Type gedit comments.pl & and press Enter.	And Type - gedit commentsExample dot pl & and press Enter.
Type # Here I am going to explain commenting in Perl # Following is the scalar variable declaration $firstNum = 10; $secondNum = 20; =head following piece of code adds 2 numbers puts the result into a 3rd variable and prints this 3rd variable =cut $addition = $firstNum + $secondNum; print “Addition is $addition”;	Type the following commands as shown on the screen. Here I am declaring two variables firstNum and secondNum and I am assigning some values to them. Then I have commented this portion here. Now I added these two numbers and assign the value to a third variable named addition. Next I want to print the value using print command.
Save the file and switch to the Terminal. Type perl -c comments.pl perl comments.pl	Save the file and execute the Perl script on the Terminal. On terminal type perl hyphen c commentsExample dot pl press enter There is no syntax error so execute the script by typing perl commentsExample dot pl press enter
Point to the output	It will show the following output. Addition is 30
Summary	This brings us to the end of this tutorial. Here we learnt, To Add Comments in Perl
Assignment	Assignment Write a perl script to find square of a number. Explain the functionality of the code written using: Single Line Comment. Mutli Line Comment.
About the Project	Watch the video available at the following link It summarises the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it
Spoken Tutorial Workshops	The Spoken Tutorial Project Team Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to contact at spoken hyphen tutorial dot org
Acknowledgment	Spoken Tutorial Project is a part of the Talk to a Teacher project It is supported by the National Mission on Education through ICT, MHRD, Government of India More information on this Mission is available at the following link.
	Hope you enjoyed this Perl tutorial. This is Amol Brahmankar signing off. Thanks for joining.

Contributors and Content Editors

AmolBrahmankar, Nancyvarkey, Sneha