Perl | Modules
A module in Perl is a collection of related subroutines and variables that perform a set of programming tasks. Perl Modules are reusable. Various Perl modules are available on the Comprehensive Perl Archive Network (CPAN). These modules cover a wide range of categories such as network, CGI, XML processing, databases interfacing, etc.
A modules name must be same as to the name of the Package and should end with .pm extension.
Example : Calculator.pm
package Calculator; # Defining sub-routine for Multiplicationsub multiplication{ # Initializing Variables a & b $a = $_[0]; $b = $_[1]; # Performing the operation $a = $a * $b; # Function to print the Sum print "\n***Multiplication is $a";} # Defining sub-routine for Divisionsub division{ # Initializing Variables a & b $a = $_[0]; $b = $_[1]; # Performing the operation $a = $a / $b; # Function to print the answer print "\n***Division is $a";}1; |
Here, the name of the file is “Calculator.pm” stored in the directory Calculator. Notice that 1; is written at the end of the code to return a true value to the interpreter. Perl accepts anything which is true instead of 1
To import this calculator module, we use require or use functions. To access a function or a variable from a module, :: is used. Here is an example demonstrating the same:
Examples: Test.pl
#!/usr/bin/perl # Using the Package 'Calculator'use Calculator; print "Enter two numbers to multiply"; # Defining values to the variables$a = 5;$b = 10; # Subroutine callCalculator::multiplication($a, $b); print "\nEnter two numbers to divide"; # Defining values to the variables$a = 45;$b = 5; # Subroutine callCalculator::division($a, $b); |
Output:
Variables from different packages can be used by declaring them before using. Following example demonstrates this
Examples: Message.pm
#!/usr/bin/perl package Message; # Variable Creation$username; # Defining subroutinesub Hello{ print "Hello $username\n";}1; |
Perl file to access the module is as below
Examples: variable.pl
#!/usr/bin/perl # Using Message.pm packageuse Message; # Defining value to variable$Message::username = "Geeks"; # Subroutine callMessage::Hello(); |
Output:
Perl provides various pre-defined modules which can be used in the Perl programs anytime.
Such as: ‘strict’, ‘warnings’, etc.
Example:
#!/usr/bin/perl use strict;use warnings; print" Hello This program uses Pre-defined Modules"; |
Output:
Hello This program uses Pre-defined Modules
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