First off: you absolutely must use strictures (use strict; use warnings;). You have a large number of errors in your code that strictures would have picked up. Aside from that the code doesn't look very Perlish in places and looks fairly newbieish in other places. The following code may be of interest:

use strict;
use warnings;

my $key = "";

while (length ($key) < 4) {
    print "Please Enter Your Desired Key (5 or more characters) \n -->
+ : ";
    $key = <>;
    chomp $key;
}

my @karray = split (//, $key);
my @offset1;
my @offset2;


for my $ordChar1 (map {ord} @karray) {
    my $sum = 0;

    for my $ordChar2 (map {ord} @karray) {
        $sum += $ordChar1 + ord $ordChar2;
        push @offset1, ($ordChar1 + $ordChar2) % 256;
    }

    push @offset2, int ($sum / length $key) % 256;
}

1 while prompt ();


sub prompt {
    my ($mode, $offset1, $offset2) = @_;

    print "Encrypt or Decrypt (E/D)\n --> :";

    my $inp = <>;

    chomp $inp;
    return 1 if $inp !~ s/^(e|d)$/lc $1/ie;

    print "Enter ", ($inp eq 'e' ? 'plain text' : 'cypher text'), "\n 
+--> : ";
    chomp (my $text  = <>);

    my @chars = split (//, $text);

    if ($inp eq 'e') {
        print encrypt(\@chars, \@offset1, \@offset2);
    } else {
        print decrypt(\@chars, \@offset1, \@offset2);
    }

    return;
}


sub encrypt {
    my ($chars, $offset1, $offset2) = @_;
    my $outText;
    my $len = @$chars;

    for my $index (0 .. $len - 1) {
        $outText .= chr ((
                ord ($chars->[$index]) -
                    ord ($offset1->[$index % $len * $len]) +
                    ord ($offset2->[$index % $len])
            ) % 256 - $index % 6);
    }

    return $outText;
}


sub decrypt {
    my ($chars, $offset1, $offset2) = @_;
    my $outText;
    my $len = @$chars;

    for my $index (0 .. $len - 1) {
        $outText .= chr ((
                ord ($chars->[$index]) +
                    ord ($offset1->[$index % $len * $len]) -
                    ord ($offset2->[$index % $len])
            ) % 256 + $index % 6);
    }

    return $outText;
}
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.