PERL Chapter -- 3



Skip to Chapter   1  2  3  4 

                                                              Chapter 3 -- Loops





The print Command

Before we go any further you should know how to use the print command.
The print command writes text to your prompt screen. You would use it by typing print "" and putting what ever you want to output in the quotes.
You can display the value of the scalar variable $snerble by entering print "$snerble";
This may seem a little weird for those of you who have programmed before, but perl does like it variables inside of the quotes.

The while Loop

The while loop allows the programmer to run a certain amount of code while a certain condition is true.
An analogy to the real world would be: While I am programming I pretend to think.
So, I would continually pretend to think as long as I am programming.
If you wanted the program to run a loop until it counted to 20 you would type:
$varname=1;
while($varname<=20)
{
print "$varname";
$varname++;
}
The line with $varname++; increases the value of $varname to one above what it used to be.

The For Loop

The for loop allows us to make a certain amount of code run a certain number of times while changing the value of a variable with each loop.
...okay, mabey you should read that above sentence a few times slowly.
A good example of the for loop is one that counts up to 100.

Example:
for($i = 0; $i <= 100; $i++)
{
print "\nThis is line $i, enjoy!";
}

The foreach Loop

This last loop is a lazy way of changing or getting the values from an entire array.
For each element in an array this loop executes a certain amount of code.

Example

@turtle = (4.5,4.2,"narf","zonk","5th element");
foreach $glerb (@turtle)
{
print("gerbil $glerb ");
}
Chapter 4 is about getting input from the user and storing it in a file.
Variables Loops Writing to Files
Skip to Chapter   1  2  3  4