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Welcome to the spoken tutorial on for and foreach Loops in Perl

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In this tutorial, we will learn about: for loop in Perl and

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foreach loop 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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If not, please go through the relevant spoken tutorials on the spoken tutorial website.

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Perl provides a mechanism by which we can check a condition repeatedly for various values. This is done using loops.

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There are various types of loops in Perl;

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for loop

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foreach loop

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while loop &

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do-while loop

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In this tutorial, we'll cover for and foreach loop.

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for loop in Perl can be used to execute a piece of code for a certain number of times.

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The syntax of for loop is as follows:

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for space open bracket variable initialization semicolon condition semicolon increment

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close bracket Press Enter

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Open curly brackets

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Piece of code to be executed multiple times

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Close curly brackets

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Now let us look at an example of a for loop.

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Open the Terminal and type; gedit forLoop.pl space & (ampersand)

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and press Enter

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This will open the forLoop.pl file in gedit.

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Type the following piece of code;hash exclamation mark slash u s r slash bin slash perl

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Press Enter

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for space open bracket dollar i equals to zero semicolon space dollar i less than or equal to four semicolon space dollar i plus plus close bracket

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space

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Open curly bracket  press enter

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typeprint space double quote Value of i colon space dollar i slash n close double quote semicolon

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And Press Enter

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now close curly bracket

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Press Ctrl+S to save the file.

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Let me explain what the for loop does.

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The variable i is initialized to zero.

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Next, the condition is checked.

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In this case, the condition is i less than or equal to 4.

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If this condition is true, the code within the curly bracket will be executed.

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This means the first print statement  "Value of i colon 0"

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will be displayed on the terminal.

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After this, the variable i is incremented by 1.

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And the for loop condition is checked once again.

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This loop will exit when the value of i becomes greater than 4.

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In this case, the for loop will be executed for i = 0, 1, 2, 3, 4

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which is a total of 5 times.

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Now, switch to  terminal.

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

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perl hyphen c forLoop dot pl

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and press Enter.

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Here it displays a message

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forLoop.pl syntax OK

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So, we have no errors.

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

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The following output will be shown on terminal.

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Now, let us look at  foreach loop.

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If we want to iterate a condition for an array, we can make use of foreach loop.

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The syntax is: foreach space dollar variable space within brackets at the rate array  space

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open curly bracket

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perform action on each element of an array  Press Enter

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Close the curly bracket.

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Please note: We'll cover array, array initialization and defining an array in subsequent tutorials.

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Now let us look at an example of foreach loop.

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Open the Terminal and type gedit foreachLoop dot pl space ampersandand Press Enter

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This will open the foreachLoop.pl file in gedit.

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Type the following piece of code

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hash exclamation mark slash u s r slash bin slash perl and Press Enter

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at the rate myarray space is equal to space open bracket ten comma twenty comma  thirty close bracket semicolon

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press enter

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foreach space dollar var space open bracket at the rate myarray close bracket space

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Open curly bracket  press enter and type

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'print space double quote Element of an array is colon dollar var  slash n close double quote  semicolon

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Press Enter and Close the curly bracket

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Press ctrl+s to save the file.

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Let me explain what this code does. An array myarray is declared.

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It has 3 elements 10, 20 and 30.

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In each iteration of foreach loop dollar var will contain the single element of an array

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foreach keyword will repeat this loop for each element of an array.

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That is, the code within the curly bracket will be executed for each myarray element.

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Back-slash n will place the prompt on a new line.

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This means the first element '10' will be displayed on the terminal.

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Then 20 and so on, till all the elements are printed.

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This loop will exit after printing all the elements in myarray.

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Now, switch to terminal and type the following to check for any compilation or syntax error.

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type perl hyphen c foreachLoop dot pland press Enter.

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The following line will be shown on terminal

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There are no compilation or syntax errors.

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So let us execute the Perl script.

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Type  perl foreachLoop dot pl and press Enter

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The following output will be shown on terminal.

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So, that's it about for loop and foreach loop.

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Let us summarize.

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In this tutorial, we have learnt -

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for loop and foreach loop in Perl

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using some sample programs.

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Here is an assignment for you -

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Declare a string as 'Spoken Tutorial' and

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Print it 5 times

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Declare an array of colors as @colorArray = open bracket in single quote red comma white comma  blue close the bracket and

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Print the element of an array using foreach loop

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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  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 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 signing off.

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Thanks for joining.