#!usr/bin/perl 
use warnings;
 
@array=qw/a b c d/; 
# Code for taking out each element: 

foreach $item (@array) { $each_ele=$item;
  print"\n Each element: $each_ele\n"; }  

# Code ?????
............
............

exit;

##</code><code>##

Difference: 
a-b 
a-c 
a-d 
b-c 
b-d 
c-d 

Product: 
a.b
a.c
a.d 
b.c 
b.d 
c.d