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Welcome to the spoken tutorial on Variables in Perl.

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In this tutorial, we will learn about Variables in Perl

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I am using Ubuntu Linux12.04 operating system and

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Perl 5.14.2  that is, Perl revision 5 version 14 and subversion 2

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I will also be using the gedit Text Editor.

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You can use any text editor of your choice.

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Variables in Perl:

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Variables are used for storing values, like text strings, numbers or arrays.

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Once a variable is declared, it can be used over and over again in the script.

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Scalar represents a single value and can store scalars only.

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Scalar variables are declared using $ (dollar) symbol.

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Let us look at Variable Declaration:

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A variable can be declared as follows: dollar priority semicolon

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Variable names in Perl can have several formats. Variables must begin with a letter or underscore

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And may contains letters, digits, underscores or a combination of above 3.

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Variables declared with CAPITAL letters have special meaning in Perl.

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So avoid declaring variables using Capital letters.

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Now open the Terminal and type  gedit variables dot pl ampersand

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The ampersand will unlock the command prompt on the terminal. Now press Enter.

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This will open the variables.pl file in gedit text editor.

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dot pl is the default extension of a Perl file.

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Type the following in the file; dollar priority semicolon and press Enter.

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So we have declared the variable priority.

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You do not need to declare a variable before using it;

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you can just use it into your code.

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Now let us assign a numerical value to the variable priority.

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For this type dollar priority space equal to space one semicolon

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and press Enter.

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Next, type

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print space double quote Value of variable is: dollar priority slash n close double quote semicolon and press enter

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slash n is the new line character.

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Now save this file as variables.pl at any location.

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In my case, it will get saved in home/amol directory. Now save this file

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Now, let us change the permissions of variables.pl  file, which we just now created.

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To do so, on the Terminal type, chmod 755 variables dot pl

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This will provide read, write & execute rights to the file.

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To compile this Perl script, on the Terminal

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type;perl hyphen c variables dot pl

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Hyphen c switch compiles the Perl script for any compilation/syntax error.

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Now press Enter

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This tells us that there is no syntax error in our script.

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Now let's execute the Perl script by typing perl variables dot pl and press Enter.

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The output displayed is as highlighted.

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We can also assign a string value to the variable we declared.

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Switch back to the Text editor window.

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Instead of dollar priority equal to one;  type

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dollar priority equal to in single quote high

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Please note that  the assignments are evaluated from right to left.

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A scalar can hold data of any type, be it a string, a number

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Save this file and compile the script once again by typing

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perl hyphen c variables dot pl now press Enter.

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This tells us that there is no syntax error.

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Execute the script by typing perl variables dot pl and press Enter.

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The output is as shown.

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Now switch back to the Text Editor window.

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You can also use scalars within a double-quoted strings as

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dollar priority in double quote String

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Save this file and close it.

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let us learn how to declare multiple variables.

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To do so open the new file in Text Editor.

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onTerminal type - gedit multivar dot pl space ampersand and press Enter.

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This will open multivar dot pl file in text editor

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Now  type -

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dollar firstVar comma dollar secondVar semicolon and press Enter.

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To copy the value of variable dollar firstVar to dollar secondVar, type -

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dollar firstVar space equal to space dollar secondVar semicolon and press Enter.

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All mathematical operations like addition, subtraction, multiplication, division, can be done on these variables

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Let us see how we can achieve this using Perl.

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Switch to text editor.

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And now let us assign the value 10 to both of these variables by typing,

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dollar firstVar equal to dollar secondVar equal to ten semicolon And Press Enter.

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Now to print these values, type

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print double quote firstVar: dollar firstVar and secondVar: dollar secondVar slash n close double quote  semicolon press Enter.

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Now save this file.

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Now let us add the values in the two variables.

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For this type

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dollar addition space equal to space dollar firstVar plus space dollar secondVar semicolonand Press Enter.

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Notice, we haven't declared the variable addition.

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Once again, to print the value of the  variable  addition, type

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print double quote Addition is dollar addition slash n close  double quote  semicolon

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Save this file

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To compile this file again on terminal type

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perl hyphen c multivar dot pl

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There is no syntax error so we can execute the script...

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by typing perl multivar dot pl

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This will produce an output as highlighted.

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Similarly, try subtraction, multiplication and division.

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I have written the code here.

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Now let us save this file and close it.

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Now compile the file by typing

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perl hyphen c multivar dot pl

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There is no syntax error.

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So we can execute the script as perl multivar dot pl

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On execution the output will look like this.

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This brings us to the end of this tutorial.

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In this tutorial we have learnt,

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To Declare and Use scalar variables in Perl

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Assignment

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Declare a number variable.

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Assign   10 to it.

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Print the variable declared.

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Declare 2 string variables.

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Assign these values to them - “Namaste ” and “India”.

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Print those 2  variables one after the other.

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Watch the video available at the following link

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It summarises the Spoken Tutorial project

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If you do not have good bandwidth, you can  download and watch it

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The Spoken Tutorial Project Team

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Conducts workshops using spoken tutorials

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Gives certificates to those who pass an online  test

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For more details, please write to  contact at spoken tutorial dot org

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Spoken Tutorial Project is a part of the Talk to a  Teacher project

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It is supported by the National Mission on  Education through ICT, MHRD, Government of India

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More information on this Mission is available  at the following link.

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Hope you enjoyed this Perl tutorial. This is Amol Brahmankar signing off.

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Thanks for joining.