**Perl** has a class-based  Object-Oriented (OO) structure that gives us the flexibility to use various new features, such as packages and modules, in Perl.

A **package** is a collection or code group in Perl. Meanwhile, a **module** in Perl is a package defined in a file with the name "package" and the the extension `.pm.`

We can only define the package once in a program; whereas, more than one different module can have the same name in a single code file.

# Code
## Perl package

A package name must always be at the start of a Perl program.

Consider the following code syntax with two #key# subroutines: blocks of code that can be reused across programs. #key# (`Car` and `Motorbike`), and a `Vehicle` package at the top of the code file.

# Package definition
package Vehicle;

sub Car{
  print "This is a car subroutine!\n";
}

sub Motorbike{
  print "This is a motorbike subroutine!\n";
}

## Perl module

The following example shows how to import a package into our code file with the `use` keyword.

# Using package Vehicle
use Vehicle;

# Function Car of vehicle
Vehicle::Car();

# Function Motorbike of vehicle
Vehicle::Motorbike();


## Perl `BEGIN` and `END` modules

Perl provides some built-in modules that include `BEGIN` and `END.` We use these modules to run certain pieces of code at the beginning and end of a program.

The following code snippet includes the `BEGIN` and `END` modules. Upon looking at the code it might seem that the `print` statement inside `END` would display first; but, if we run this code, it will be displayed at the end. 

The code below shows how this keyword works.

BEGIN{
  print "Beginning of the program\n";
}

END{
  print "Ending of the program\n";
}

print "Begin and End modules in Perl!\n";

What are packages and modules in Perl?

Perl's OO structure includes packages (code groups) and modules (packages in .pm files), with BEGIN and END modules running code at program start and end.

What are packages and modules in Perl?

Code

Perl package

Perl module

Perl BEGIN and END modules

Perl `BEGIN` and `END` modules