my ($a, $b, $c, $d) = 'abcd' =~ /(w)(x)(y)(z)/;
{
    no warnings 'uninitialized';
    print "$a $b $c $d";
}

##</code><code>##

printf "%s %s %s %s\n", $a//'', $b//'', $c//'', $d//'';

##</code><code>##

my ($a, $b, $c, $d) = ( 'abcd' =~ /(w)(x)(y)(z)/, '','','','' );