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Time Narration
00:01 Welcome to the spoken tutorial on Variables in Perl.
00:06 In this tutorial, we will learn about variables in Perl.
00:12 I am using Ubuntu Linux12.04 operating system and
00:18 Perl 5.14.2 that is: Perl revision 5, version 14, and subversion 2.
00:26 I will also be using the gedit Text Editor.
00:30 You can use any text editor of your choice.
00:34 Variables in Perl:
00:37 Variables are used for storing values like text strings, numbers or arrays.
00:44 Once a variable is declared, it can be used over and over again in the script.
00:50 Scalar represents a single value and can store scalars only.
00:56 Scalar variables are declared using $ (dollar) symbol.
01:00 Let us look at variable declaration.
01:03 A variable can be declared as follows: dollar priority semicolon.
01:09 Variable names in Perl can have several formats. Variables must begin with a letter or underscore (_).
01:18 And may contain letters, digits, underscores or a combination of above three.
01:24 Variables declared with CAPITAL letters have special meaning in Perl.
01:30 So, avoid declaring variables using capital letters.
01:34 Now open the Terminal and type: gedit variables dot pl ampersand(&)
01:44 The ampersand will unlock the command prompt on the terminal. Now press Enter.
01:50 This will open the file in gedit text editor.
01:56 dot pl (.pl) is the default extension of a Perl file.
02:01 Type the following in the file: dollar priority semicolon and press Enter.
02:10 So we have declared the variable priority.
02:13 You do not need to declare a variable before using it;
02:18 you can just use it into your code.
02:21 Now let us assign a numerical value to the variable priority.
02:25 For this, type: dollar priority space equal to space one semicolon
02:32 and press Enter.
02:34 Next, type:
02:36 print space double quote Value of variable is: dollar priority backslash n close double quote semicolon and press Enter.
02:50 backslash n is the "new line" character.
02:53 Now save this file as at any location.
03:02 In my case, it will get saved in home/amol directory. Now save this file.
03:10 Now, let us change the permissions of file which we just now created.
03:18 To do so, on the Terminal type, chmod 755 variables dot pl
03:27 This will provide "read", "write" & "execute" rights to the file.
03:32 To compile this Perl script, on the Terminal,
03:36 type: perl hyphen c variables dot pl
03:42 Hyphen c switch compiles the Perl script for any compilation/syntax error.
03:49 Now press Enter.
03:51 This tells us that there is no syntax error in our script.
03:56 Now let us execute the Perl script by typing perl variables dot pl and press Enter.
04:06 The output displayed is as highlighted.
04:10 We can also assign a string value to the variable we declared.
04:15 Switch back to the Text editor window.
04:18 Instead of dollar priority equal to one; type:
04:22 dollar priority equal to in single quotes high;
04:28 Please note that the assignments are evaluated from right to left.
04:34 A scalar can hold data of any type, be it a string, a number.
04:38 Save this file and compile the script once again by typing:
04:45 perl hyphen c variables dot pl now press Enter.
04:51 This tells us that there is no syntax error.
04:55 Execute the script by typing perl variables dot pl and press Enter.
05:03 The output is as shown.
05:07 Now switch back to the Text Editor window.
05:10 You can also use scalars within a double-quoted string as
05:15 dollar priority in double quotes string;
05:19 Save this file and close it.
05:22 Let us learn how to declare multiple variables.
05:27 To do so, open the new file in Text Editor.
05:31 OnTerminal, type: gedit multivar dot pl space ampersand and press Enter.
05:42 This will open "multivar dot pl" file in text editor.
05:48 Now, type:
05:50 dollar firstVar comma dollar secondVar semicolon and press Enter.
06:00 To copy the value of variable dollar firstVar to dollar secondVar, type:
06:07 dollar firstVar space equal to space dollar secondVar semicolon and press Enter.
06:19 All mathematical operations like addition, subtraction, multiplication, division, can be done on these variables.
06:30 Let us see how we can achieve this using Perl.
06:34 Switch to text editor.
06:36 And now let us assign the value 10 to both of these variables by typing,
06:41 dollar firstVar equal to dollar secondVar equal to ten semicolon and press Enter.
06:51 Now, to print these values, type:
06:55 print double quote firstVar: dollar firstVar and secondVar: dollar secondVar backslash n close double quotes semicolon press Enter.
07:17 Now save this file.
07:19 Now, let us add the values in the two variables.
07:23 For this, type:
07:25 dollar addition space equal to space dollar firstVar space plus space dollar secondVar semicolon and Press Enter.
07:43 Notice, we haven't declared the variable addition.
07:47 Once again, to print the value of the variable addition, type:
07:53 print double quote Addition is dollar addition backslash n close double quote semicolon.
08:05 Save this file.
08:07 To compile this file, again on terminal type:
08:12 perl hyphen c multivar dot pl
08:18 There is no syntax error, so we can execute the script
08:24 by typing perl multivar dot pl.
08:30 This will produce an output as highlighted.
08:34 Similarly, try subtraction, multiplication and division.
08:38 I have written the code here.
08:41 Now, let us save this file and close it.
08:46 Now compile the file by typing
08:48 perl hyphen c multivar dot pl
08:54 There is no syntax error. So, we can execute the script as perl multivar dot pl
09:01 On execution, the output will look like this.
09:06 This brings us to the end of this tutorial.
09:11 In this tutorial, we have learnt
09:14 to declare and use scalar variables in Perl.
09:18 Assignment:
09:20 Declare a number variable.
09:22 Assign 10 to it.
09:24 Print the variable declared.
09:26 Declare 2 string variables.
09:29 Assign these values to them - “Namaste ” and “India”.
09:34 Print those two variables one after the other.
09:38 Watch the video available at the following link.
09:42 It summarizes the Spoken Tutorial project.
09:45 If you do not have good bandwidth, you can download and watch it.
09:50 The Spoken Tutorial Project Team:
09:53 Conducts workshops using spoken tutorials.
09:56 Gives certificates to those who pass an online test.
10:01 For more details, please write to contact at spoken tutorial dot org.
10:08 Spoken Tutorial Project is a part of the Talk to a Teacher project.
10:13 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:23 More information on this mission is available at the following link.
10:29 Hope you enjoyed this Perl tutorial. This is Amol Brahmankar, signing off.
10:34 Thanks for joining.

Contributors and Content Editors

Gaurav, Madhurig, PoojaMoolya, Sandhya.np14, Sneha