This behavior appears somewhere between versions 5.12.3 and 5.14.4, but a quick scan of the deltas (update: between these versions) shows no justification for it. (Update: All code run under Windows 7.)

c:\@Work\Perl\monks>perl -wMstrict -le
"print 'perl version: ', $];
 ;;
 use Data::Dumper;
 ;;
 @_ = qw( a b c );
 print( ( shift @_ )[ 0, 0, 0 ] );
 ;;
 @_ = qw( a b c );
 my @A = ( shift @_ )[ 0, 0, 0 ];
 print Dumper \@A;
 ;;
 @A = ( 'x', 'y', 'z' )[ 0, 0, 0 ];
 print Dumper \@A;
"

perl version: 5.012003
aaa
$VAR1 = [
          'a',
          'a',
          'a'
        ];

$VAR1 = [
          'x',
          'x',
          'x'
        ];

perl version: 5.014004
aaa
$VAR1 = [
          'a',
          undef,
          undef
        ];

$VAR1 = [
          'x',
          'x',
          'x'
        ];
[download]

Version 5.14 is the latest I can access ATM.