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 }