Caesar Cipher script and class

SCRIPT

#!/usr/bin/perl -w

use strict;
use warnings;
use feature 'say';
use Switch;

use Crypt::CaesarCipher;
my $shiftValue='3';

my $plainText;
switch (defined($ARGV[0])) {
    case '' {
        $plainText='workshop at unina mmxiv'
    }
    else {
        $plainText=$ARGV[0]
    }
}

say '--> Testo in chiaro: '.$plainText;

# istanza oggetto cifrario di Cesare
my $caesarCipher=Crypt::CaesarCipher->new({setShift => $shiftValue});

# invocazione metodo di cifratura
my $encrypted=$caesarCipher->encrypt($plainText);
say '--> Messaggio criptato '.$encrypted;

# decifrazione del messaggio criptato
my $decrypted=$caesarCipher->decrypt($encrypted);
say '--> Messaggio decriptato '.$decrypted;

CLASSE Crypt::CaesarCipher

# package Caesar Cipher by [email protected] - CC-BY-SA
package Crypt::CaesarCipher;

use strict;
use warnings;
use base 'Class::Accessor';

Crypt::CaesarCipher->mk_accessors('encrypt','decrypt','setShift');
our $VERSION='0.01';

# ascii a = 97 e ascii z= 122

sub encrypt {
    my ($self,$plainText)=@_;
    my $encryptedText;

    foreach my $plainChar(split //,$plainText) {
        my $ordCharShifted=ord($plainChar)+$self->setShift;
        if ($ordCharShifted > 122) {
            $encryptedText.=chr($ordCharShifted - 122 + 96)
        } else {
            $encryptedText.=chr($ordCharShifted)
        }
    }
    return $encryptedText
}

sub decrypt {
    my ($self,$encryptedText)=@_;
    my $plainText;

    foreach my $encryptedChar(split //,$encryptedText) {
        my $ordCharShifted=ord($encryptedChar)-$self->setShift;
        if ($ordCharShifted < 97) {
            $plainText.=chr(122 - $ordCharShifted + 96)
        } else {
            $plainText.=chr($ordCharShifted)
        }
    }
    return $plainText
}
1;