%tmp= (nothing => undef, one => 1); # $tmp{nothing} is undef %tmp= (nothing => (0, undef)[0], one => 1); # $tmp{nothing} == 0 %tmp= (nothing => [undef, 0]->[0], one => 1); # $tmp{nothing} is undef %tmp= (nothing => scalar ((0, undef)[1]), one => 1); # $tmp{nothing} is undef %tmp= (nothing => (undef), one => 1); # $tmp{nothing} is undef %tmp= (nothing => (undef)[0], one => 1); # $tmp{nothing} eq 'one'*** Why not undef? %tmp= (nothing => (undef, 0)[0], one => 1); # $tmp{nothing} eq 'one'*** Why not undef? 1;