Thank you all for your assistance, from the suggestions I've gotten from here and over on the Perl board at HackForums I've made a few updates. I'm yet to include structures but have practised using them as evident in a poem I'm about to upload. I think I'm going to enjoy it here. Very quick, detailed responses and wonderfully helpful insight.

 
##Authored by Troy Osborne (Pseudomander) 4:45am 25/02/2012 AEST +10 #
+#

##Free to redistribute, use, copy, upload & adapt this work, all I ask
+ is if it in anyway represents the original version please give credi
+t where due##



use warnings;



$key="";

$offsetpattern="";

$offsetpattern2="";

while (length($key) < 4)

{

    print "Please Enter Your Desired Key (5 or more characters) \n -->
+ :";

    chomp($key=<>);

}

@karray= split(//,$key);

for ($i=0;$i<length($key);$i++)

{

    $temp =0;

    for ($i2=0;$i2<length($key);$i2++) 

        {    

            $temp += (ord($karray[$i])+ord($karray[$i2]));

            $offsetpattern .= chr((ord($karray[$i])+ord($karray[$i2]))
+%256);

        }

    $offsetpattern2.=chr(int($temp /length($key))%256);

}

@offset = split(//,$offsetpattern);

@offset2 = split(//,$offsetpattern2);





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

$inp=<>;

if (($inp=~/E/) or ($inp=~/e/))

#Encryption

{

    print "Enter Plaintext\n --> :";

    chomp($plaintext = <>); 

    $len = length($plaintext)-1;

    @array = split(//, $plaintext);

    for ($i=0;$i<$len;$i++)

    {

        $char = chr((ord($array[$i]) - ord($offset[$i % length($key)*l
+ength($key)])+ ord($offset2[$i % length($key)]))%256);

        print chr(ord($char)-($i%6));

    }

}

elsif (($inp=~/D/) or ($inp=~/d/))

#Decryption

{

    print "Enter Cyphertext\n --> :";

    chomp($cyphertext = <>);

    $len = length($cyphertext)-1;

    @array = split(//, $cyphertext);

    for ($i=0;$i<$len;$i++)

    {

        $char = chr((ord($array[$i]) + ord($offset[$i % length($key)*l
+ength($key)]) - ord($offset2[$i % length($key)]))%256);

        print chr(ord($char)+($i%6));

    }

}

<>;
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