use strict;
use warnings;

my @stuff = (0,1, undef);

for (0..3)
{
	print "Element $_ : " . 
	(!exists ($stuff[$_]) ? 'Does not exist' :
	!defined ($stuff[$_]) ? 'is Undef' :
	"is '$stuff[$_]'")
	. "\n";	
}
##</code><code>##

>perl test.pl
Element 0 : is '0'
Element 1 : is '1'
Element 2 : is Undef
Element 3 : Does not exist