use strict;
use warnings;

$" = '+';

for( 
    ['a', 'b'], 
    [1, 2], 
    [0, 1], 
    ['a', 'b'], 
    [undef, undef], 
    [1, undef], 
    [undef, 1], 
    [ ],
) {
    print "\@\$_ is @$_\n";
    (my ($foo, $bar) = @$_)
        || print "I would die here\n";
    print "\n";
}