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Welcome to the spoken tutorial on if and if-else conditional statements in Perl.

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In this tutorial, we will learn about;

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if  statement and

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if-else statement in Perl

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I am using Ubuntu Linux12.04 operating system and Perl 5.14.2

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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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You should have basic knowledge of Variables and Comments in Perl.

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Knowledge of for, foreach , while and  do-while loops in Perl will be an added advantage.

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Please go through the relevant spoken tutorials on the spoken tutorial website.

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Perl provides the following conditional statements -

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if

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if-else

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if-elsif-else and

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switch

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In this tutorial, we'll cover if and If-else statements

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if  statement in Perl can be used

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to execute a piece of code only when a specified condition is satisfied.

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The syntax of if conditional statement is as follows

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if space open bracket condition close bracket space Open curly bracket

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Enter

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Piece of code semicolon,  to be executed when the condition is true

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Enter, Close curly bracket

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The code inside the if statement will be executed only when the condition is true.

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Now let us look at an example of if  statement.

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Open the Terminal and type

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gedit conditionalBlocks dot pl  space &(ampersand )

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and press Enter

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This will open the conditionalBlocks.pl file in gedit.

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Type the following piece of code as displayed on the screen.

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Here we have specified a condition for if which checks the value of variable count.

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Note the equal to equal to sign here. This is the comparison operator.

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The condition $count equal to equal to 5  is checked against the value of variable count.

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When it is equal to 5, the code within the if block will get executed.

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Now, press ctrl+s to save the file.

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Then switch to the terminal.

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Make sure that you are in the directory in which you have saved your file.

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Type the following to check for any compilation or syntax error -

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perl hyphen c conditionalBlocks dot pl

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and press Enter.

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The following line will be displayed on the terminal window

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conditionalBlocks.pl syntax OK

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As there is no compilation or syntax error, we will execute the Perl script by typing -

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perl conditionalBlocks dot pl

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and press Enter

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The following output will be shown on terminal.

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I am inside if statement

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Switch back to gedit

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Alternately, we can write the above  if statement as-

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print  space double quotes I am inside if statement slash n close double quotes  space if open bracket dollar count space equal to equal to space 5 close bracket semicolon.

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Now, let us look at if-else statement.

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This statement is used when user wants to execute

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one piece of code when the condition is true and

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another piece of code when the condition is false

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The syntax for if-else condition is as follows -

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if  space open bracket condition close bracket space open curly bracket Press Enter.

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piece of code semicolon

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to be executed when if condition is true,

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Press Enter

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close curly bracket space else space open curly bracket Enter

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another piece of code semicolon

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to be executed when if condition is false

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Press Enter close curly bracket

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Now again, go to the conditionalBlocks.pl file which we have already created in gedit.

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Assign 4 to count variable then at the end of the if block type space

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else

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space open curly bracket press Enter

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print space double quotes I am inside else statement slash n close double quotes  semicolon

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Press Enter and close  curly bracket.

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Here, 4 is assigned to variable $count.

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As the value of count variable does not match 5,

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the code within the if block will not get execute

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instead the code within the else block will get execute.

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Now press  Ctrl+S to save the file.

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Now switch to terminal.

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and type perl hyphen c conditionalBlocks dot pl to check for any compilation or syntax error

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now, press Enter

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The following line will be displayed on the terminal

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conditionalBlocks.pl syntax OK

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As there is no compilation or syntax error, we will now execute the Perl script.

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Type perl conditionalBlocks dot pl

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and press Enter

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The following output will be shown on terminal.

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I am inside else statement

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Let us summarize.

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In this tutorial, we have learnt -

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if and

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if-else conditional statements in Perl

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using sample programs.

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Here is assignment for you -

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Print  “It is an open source language”

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when the variable declared has value  'Perl'

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otherwise print  “It's a proprietary language”

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Watch the video available at the following link

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It summaries 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 hyphen 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 spoken hyphen tutorial dot org slash NMEICT hyphen Intro

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Hope you enjoyed this Perl tutorial.

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This is Amol Brahmankar signing off.

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Thanks for joining.