Listing Even Numbers in Perl

What are Even Numbers?

Hello pupils, what are even numbers?
Answer:
Even numbers are numbers that are divisible by 2.

They include:

2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, ...

Well then, let's see how we can write a programming code to make our computer list a set of even numbers in the Perl language, between a given range of values.

Create a new Perl Class File; call it Arithmetic.pl.
Create a new Perl Module File; call it evenNumbers.pm.

Type out the adjoining Perl code that list even numbers.
We will see what each significant part does as we go along.

How to run Perl Codes

Run the code from the cmd shell with the command: cd ~/Documents/usingMaths -- to navigate to the folder where you saved your files;
perl Arithmetic.pl

Perl code for evenNumbers Module File.

package EVENNUMBERS;

BEGIN {
    require Exporter;

    # for the sake of standard
    our $VERSION = 2016.12;

    # Inherit from exporter to export functions and variables
    our @ISA = qw(Exporter);

    # Functions and variables to be exported by default
    our @EXPORT_OK = qw(prepResult);
}

use warnings;
use strict;

my ($start, $stop);
my @result;

# simulate an object construct
# takes two arguments  -- besides its name;
# start and stop values for the range
sub new {
    my $this = shift;
    my $parameters = {@_};
    bless $parameters, $this;
    $this->_init(@_);
    return $this;
}

# Simulate a constructor
sub _init {
    my $self = shift;
    ($start, $stop) = @_;
}

# Returns an array reference of the desired set of even numbers
sub prepResult {
    # Loop from start to stop and rip out even numbers;
    until ($start > $stop) {
        if (($start % 2) == 0) { # modulo(%) is explained later
            push @result, $start;
        }
        $start = $start + 1; # increase start by 1
    }
    return \@result;
}

1;

Main class code.

#!/usr/bin/perl;
use strict;
use warnings;
use EVENNUMBERS;

# Useful variables
my ($lower_boundary, $upper_boundary, $answer);

# Use the even number module/class
$lower_boundary = 1;
$upper_boundary = 100;
my $even_list = EVENNUMBERS->new($lower_boundary, $upper_boundary);
$answer = $even_list->prepResult();
print "Even numbers between $lower_boundary and $upper_boundary are:\n@{$answer}\n";

print "\n\n";

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