Here is a piece of code that I wrote about two years ago which does this (and more). Feel free to adjust it for your needs: 
use 5.010;
use strict;
use warnings;

sub encode_decode ($$) {
    my ($encode, $text) = @_;

    my $i = 1;
    my $output = '';

  LOOP_1: foreach my $c (map ord, split //, $text) {
        foreach my $o ([32, 121]) {
            if ($c > $o->[0] && $c <= $o->[1]) {

                my $ord = $encode
                        ? $c + ($i % 2 ? $i : -$i)
                        : $c - ($i % 2 ? $i : -$i);

                if ($ord > $o->[1]) {
                    $ord = $o->[0] + ($ord - $o->[1]);
                }
                elsif ($ord <= $o->[0]) {
                    $ord = $o->[1] - ($o->[0] - $ord);
                }
                $output .= chr $ord;
                ++$i; next LOOP_1;
            }
        }
        $output .= chr($c);
        $i = 1;
    }

    return $output;
}

my $enc = encode_decode(1, q{this is a test});
my $dec = encode_decode(0, $enc);

say "Enc: ", $enc;
say "Dec: ", $dec;

__END__
Enc: uflo jq b ucvp
Dec: this is a test

[download]
Also, please see: http://rosettacode.org/wiki/Caesar_cipher#Perl

In reply to Re: Encryption/Decryption Program: by trizen
in thread Encryption/Decryption Program: by Perl Beginner01

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