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    detected. No action is take until a event loop is entered.

    Arguments for new are:

    dirs
            dirs => [ '/var/log', '/etc' ],

        An ArrayRef of directories to watch. Required.

    interval
            interval => 1.5,   # seconds

        Specifies the time in fractional seconds between file system checks
        for the AnyEvent::Filesys::Notify::Role::Fallback implementation.

        Specifies the latency for Mac::FSEvents for the
        "AnyEvent::Filesys::Notify::Role::FSEvents" implementation.

        Ignored for the "AnyEvent::Filesys::Notify::Role::Inotify2"
        implementation.

    filter
            filter => qr/\.(ya?ml|co?nf|jso?n)$/,
            filter => sub { shift !~ /\.(swp|tmp)$/,

        A CodeRef or Regexp which is used to filter wanted/unwanted events.
        If this is a Regexp, we attempt to match the absolute path name and
        filter out any that do not match. If a CodeRef, the absolute path
        name is passed as the only argument and the event is fired only if
        there sub returns a true value.

    cb
            cb  => sub { my @events = @_; ... },

        A CodeRef that is called when a modification to the monitored
        directory(ies) is detected. The callback is passed a list of
        AnyEvent::Filesys::Notify::Events. Required.

    backend
            backend => 'Fallback',
            backend => 'KQueue',
            backend => '+My::Filesys::Notify::Role::Backend',

        Force the use of the specified backend. The backend is assumed to
        have the "AnyEvent::Filesys::Notify::Role" prefix, but you can force
        a fully qualified name by prefixing it with a plus. Optional.

    no_external
            no_external => 1,

        This is retained for backward compatibility. Using "backend ="
        'Fallback'> is preferred. Force the use of the "Fallback" watcher
        implementation. This is not encouraged as the "Fallback" implement
        is very inefficient, but it does not require either Linux::INotify2
        nor Mac::FSEvents. Optional.

    parse_events
            parse_events => 1,

        In backends that support it (currently INotify2), parse the events
        instead of rescanning file system for changed "stat()" information.
        Note, that this might cause slight changes in behavior. In
        particular, the Inotify2 backend will generate an additional
        'modified' event when a file changes (once when opened for write,
        and once when modified).

    skip_subdirs
            skip_subdirs => 1,

        Skips subdirectories and anything in them while building a list of
        files/dirs to watch. Optional.

WATCHER IMPLEMENTATIONS
  INotify2 (Linux)
    Uses Linux::INotify2 to monitor directories. Sets up an "AnyEvent->io"
    watcher to monitor the "$inotify->fileno" filehandle.

  FSEvents (Mac)
    Uses Mac::FSEvents to monitor directories. Sets up an "AnyEvent->io"
    watcher to monitor the "$fsevent->watch" filehandle.

  KQueue (BSD/Mac)
    Uses IO::KQueue to monitor directories. Sets up an "AnyEvent->io"
    watcher to monitor the "IO::KQueue" object.

    WARNING - IO::KQueue and the "kqueue()" system call require an open
    filehandle for every directory and file that is being watched. This
    makes it impossible to watch large directory structures (and inefficient
    to watch moderately sized directories). The use of the KQueue backend is
    discouraged.

  Fallback
    A simple scan of the watched directories at regular intervals. Sets up
    an "AnyEvent->timer" watcher which is executed every "interval" seconds
    (or fractions thereof). "interval" can be specified in the constructor
    to AnyEvent::Filesys::Notify and defaults to 2.0 seconds.

    This is a very inefficient implementation. Use one of the others if
    possible.

Why Another Module For File System Notifications
    At the time of writing there were several very nice modules that
    accomplish the task of watching files or directories and providing
    notifications about changes. Two of which offer a unified interface that
    work on any system: Filesys::Notify::Simple and File::ChangeNotify.

    AnyEvent::Filesys::Notify exists because I need a way to simply tie the
    functionality those modules provide into an event framework. Neither of
    the existing modules seem to work with well with an event loop.
    Filesys::Notify::Simple does not supply a non-blocking interface and
    File::ChangeNotify requires you to poll an method for new events. You
    could fork off a process to run Filesys::Notify::Simple and use an event
    handler to watch for notices from that child, or setup a timer to check
    File::ChangeNotify at regular intervals, but both of those approaches
    seem inefficient or overly complex. Particularly, since the underlying
    watcher implementations (Mac::FSEvents and Linux::INotify2) provide a
    filehandle that you can use and IO event to watch.

    This is not slight against the authors of those modules. Both are well
    respected, are certainly finer coders than I am, and built modules which
    are perfect for many situations. If one of their modules will work for