pilsner:~ [11:58:42]$ perl -MO=Deparse -e 'while (<>) {}'
while (defined($_ = <ARGV>)) {
    ();
}
-e syntax OK
pilsner:~ [11:59:05]$ perl -MO=Deparse -e 'while (local $_=<>) {}'
while (defined(local $_ = <ARGV>)) {
    ();
}
-e syntax OK