PERL/C2/Variables-in-Perl/English-timed

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 variables.pl 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 variables.pl 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 variables.pl 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.
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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