#...
use File::Find;
#...
find ({
    wanted =>
        sub {(
            # There's an MP3!!!
            /\.mp3/i &&
            # but is it legal?
            ($host->is_legal || $host->set_illegal)
        )
    }, '/');

if ($host->illegal_file_found) {
    # Hooked another one
    $host->flag_for_lawsuit;
}
else {
    # They've got to be hiding something,
    # flag them anyways.
    $host->flag_for_lawsuit;
}
#...