Time to learn the different types of variables available within Perl.
Variables are basically handy places to store something. In other words, it is just the name of a place so you know where to find it later.
Scalar variables are identified with the '$' character infront of the variable name. So a variable with the name of "thing" would be written as $thing. You assign values to these variables by using the = operator, just like many other programming languages. All scalar variables have a singular (scalar) value to them. Scalar variables do not have to be pre-defined, as other languages usually require.
The $ identifies the variable as scalar.
Scalar Variables can also change their type during runtime, for example, say we have the variable $stuff. We can change it like so;
$stuff = "123";
print $stuff + 1 . "\n";
The scalar variable $stuff was originally a string. During the print statement though, it was converted to a number to add 1 to it, then converted back to a string. Therefore, the output would be 124.
Another thing you can do is utilize the original variable value when you redeclare that variable. Sound confusing?
Just look at the next example.
$lucky = 7;
$lucky = "My lucky number is $lucky";
This ability comes in extremely handy later on when you are making scripts.
Arrays are identified by the @ prefix. Arrays, in short, are plural versions of scalar variables. Within an array, you can store many variables. The syntax for an array is shown in the example below;
@one_to_ten =("one","two","three","four","five","six","seven","eight","nine","ten");
Perl arrays are index from the number 0 and up though. Therefore, when you want to access a single value from the array, you have to keep this in mind. Say I wanted to print the value "seven" from @one_to_ten. I would do so using the following syntax;
print "$one_to_ten[6]\n";
It's that easy. If you want to print all the values of @one_to_ten though, you will utilize the function "foreach". foreach is used like so;
foreach $number (@one_to_ten) {
print "$number\n";}
The $number part of the foreach function can be named whatever you want it to be. It is basically the reference you are using to each value of the array.
A hash is not a normal type of array, it is known as an associative array or a paired group of elements. Hash names in perl have the prefix %, or the percent sign. They consist of pairs of elements.... keys and the value. You will find an example on the most readable way to declare a hash below;
%mysite = (
"scripts" => "http://www.mysite.com/scripts/",
"forums" => "http://www.mysite.com/forums/",
"reviews" => "http://www.mysite.com/reviews/"
);
Now if I wanted to print just the "scripts" part of the mysite hash, I would do so with the following;
print "$mysite{'scripts'}\n";
If you want to print all of the values of a hash though, you will have to use the foreach function again, but a little differently;
foreach $key (keys %mysite) {
print "$key can be found at: $mysite{$key}\n";
}
Keys are the identifying element of a hash. In the %mysite, the keys are scripts, helpforums, and reviews.