my @array;
    @array[3..9] = (3,4,undef,undef,7);
    delete @array[4,8];
    print join"\n",map{defined $array[$_] 
                      ? "$_: $_"
                      : exists $array[$_]
                        ? "$_: undef-but-exists"
                        : "$_: undef-not-exists"} 0 .. 10;
    __END__
    
OUTPUT:
    0: undef-not-exists
    1: undef-not-exists
    2: undef-not-exists
    3: 3
    4: undef-not-exists
    5: undef-but-exists
    6: undef-but-exists
    7: 7
    8: undef-not-exists
    9: undef-but-exists
    10: undef-not-exists