local $/ = "\x0A\x00";
for (
    my $line = '';
    defined( $_ = <> );
    $line = ''
) {
    $line .= $_;
    redo if length($line) % 2 != 0;

    print
        pack 'C*',
        map { $_ <= 0xFF ? $_ : '?' }
        unpack 'v*',
        $line;

    #   -or-
    # print utf16le($line)->latin1();
}