c:\@Work\Perl\monks>perl -wMstrict -MData::Dumper -le
"sub modify { $_ = 5 for @_; }
 ;;
 my @a;
 @a = (undef) x 5;
 ;;
 modify(@a);
 print Dumper \@a;
 ;;
 my @b;
 $#b = 4;
 ;;
 modify(@b);
 print Dumper \@b;
 ;;
 my @c;
 $#c = 4;
 $c[ $#c ] = undef;
 ;;
 modify(@c);
 print Dumper \@c;
"
$VAR1 = [
          5,
          5,
          5,
          5,
          5
        ];

$VAR1 = [
          undef,
          undef,
          undef,
          undef,
          undef
        ];

$VAR1 = [
          undef,
          undef,
          undef,
          undef,
          5
        ];

##</code><code>##

c:\@Work\Perl\monks>perl -wMstrict -MData::Dumper -le
"my @b;
 $#b = 4;
 ;;
 $_ = 5 for @b;
 print Dumper \@b;
 ;;
 my @c;
 $#c = 4;
 $c[ $#c ] = undef;
 ;;
 $_ = 6 for @c;
 print Dumper \@c;
"
$VAR1 = [
          5,
          5,
          5,
          5,
          5
        ];

$VAR1 = [
          6,
          6,
          6,
          6,
          6
        ];