>perl -we "for(\0,0){print${$_||next}}"
0
>perl -MO=Deparse -we "for(\0,0){print${$_||next}}"
BEGIN { $^W = 1; }
foreach $_ (\0, 0) {
    print ${next unless $_;};
}
-e syntax OK

>perl -we "for(\0,0){print${next unless $_}}"
0
>