#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dump qw(pp);
 
my @array1=(1..2,"");
my @array2=(2..3,undef);
 
my (%union, %sdiff, %sd1, %sd2, %inter);
 
@union{(@array1,@array2)} = (@array1,@array2);
 
%sd1 = %sd2 = %inter = %union;
 
delete @sd1{@array2};
delete @sd2{@array1};
%sdiff = (%sd1,%sd2);
 
delete @inter{keys %sdiff};
 
print "array1: ", pp(\@array1), "\n";
print "array2: ", pp(\@array2), "\n";
print "union: ", pp(\%union), "\n";
print "sdiff: ", pp(\%sdiff), "\n";
print "inter: ", pp(\%inter), "\n";
print "sd1: ", pp(\%sd1), "\n";
print "sd2: ", pp(\%sd2), "\n";

##</code><code>##

Use of uninitialized value $array2[2] in hash slice at /home/lanx/B/PL/PM/set2.pl line 12.
Use of uninitialized value $array2[2] in delete at /home/lanx/B/PL/PM/set2.pl line 16.
array1: [1, 2, ""]
array2: [2, 3, undef]
union: { "" => undef, 1 => 1, 2 => 2, 3 => 3 }
sdiff: { 1 => 1, 3 => 3 }
inter: { "" => undef, 2 => 2 }
sd1: { 1 => 1 }
sd2: { 3 => 3 }