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What are variables in Perl?

Adnan Abbas

Variables are used to store some value. Based on the data type of the variable, the interpreter allocates memory to the variable.

All variables in Perl must be in accordance with the following rules:

  • variable names must contain only letters (a-z, A-Z), underscores (_), and numeric digits (0-9).

  • The first character of a variable name must be a letter (a-z, A-Z) or underscore (_).

  • Variable names are case-sensitive, so thiscar is not the same as ThisCar.

The basic data types in Perl are:

  • Scalars
  • Arrays
  • Hashes
%0 node_1 Mon
A Scalar variable in Perl
%0 node_1 Mon node_2 1 node_3 Tues node_1624974833571 2 node_1624974851424 Wed node_1624974910834 2
An Array in Perl
%0 node_0 Key 1 node_0_1 Val 1 node_0->node_0_1
A Hash in Perl

Example

In our examples, we will be creating variables of these three data types. A sign precedes a scalar variable, and it can store a number, string, or reference. An array variable is prefixed by @, and it stores an ordered list of scalars. Finally, the hash variable is preceded by the & and stores key-value pairs.

Creating variables

In Perl, we do not need to explicitly reserve space for the variable. Using the = operator automatically creates space when we assign a value to the variable. The operand on the left of the = operator is the variable name, and the operand on the right is the value stored in the variable.

Scalar variables

We will create three scalar variables named name, age, and gender in this example. A scalar is a single unit of data that can be of any data type, such as a character, a string, an integer, a floating point, a paragraph, or an entire web page.

$age = 15;             # An integer assignment
$name = "Usuf DePaul";   # A string 
$gender = "male";     # A string

print "Age = $age\n";
print "Name = $name\n";
print "Gender = $gender\n";
Creating scalar variables

Array variables

An array stores a list of ordered scalar variables. This example shows how we can create arrays in Perl:

We use the sign to access the elements of the array since the element is a scalar variable.

@order_nums = (1, 3, 55);             
@names = ("Jacob", "Kumar", "Dinesh");

print "\$order_nums[0] = $order_nums[0]\n";
print "\$order_nums[1] = $order_nums[1]\n";
print "\$order_nums[2] = $order_nums[2]\n";
print "\$names[0] = $names[0]\n";
print "\$names[1] = $names[1]\n";
print "\$names[2] = $names[2]\n";
Creating an array

Hash variables

A hash is a set of key-value pairs. To access the value associated with a key, we will use the hash variable name followed by the key in curly brackets:

%data = ("Jacob", 1, "Kumar", 3, "Dinesh", 55);

print "\$data{'Jacob'} = $data{'Jacob'}\n";
print "\$data{'Kumar'} = $data{'Kumar'}\n";
print "\$data{'Dinesh'} = $data{'Dinesh'}\n";
Creating a hash variable

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