#!/usr/bin/perl -w
use strict;

my @a = qw|a b c d e|;
my @b = qw|b c d c i|;

my %a = map {$_=>1} @a;
my %bank;
    for(0..$#b){
        if(defined($a{$b[$_]})){
	    $bank{$b[$_]}++;
            $a{$b[$_]}++;
            undef $b[$_];
            
        }
    }

print "NEW \@A:\t" . join ',', sort grep { $a{$_}==1 } keys %a;
print "\nNEW \@B:\t" . join ',', grep {defined($_)} @b;
print "\nINCOMMON:\t" . join ',', keys %bank;

1;
===========
C:\Temp>perl shoo.pl
NEW @A: a,e
NEW @B: i
INCOMMON:       c,b,d