If your running Win32 then Win32::ChangeNotify makes this very easy.

#! perl -slw
use strict;
use Win32::ChangeNotify;

my $path = 'p:\test';

my $notify = Win32::ChangeNotify->new( $path, 0, 'FILE_NAME' );

my %last; @last{ glob $path . '/*' } = ();

while( 1 ) {
    print('Nothing changed'), next
        unless $notify->wait( 10_000 ); # Check every 10 seconds
    $notify->reset;
    print $/, 'Something changed';
    my @files = glob $path . '/*';
    if( @files < scalar keys %last ) {
        delete @last{ @files };
        print 'These files where deleted: ';
        print for keys %last;
            print'';
    }
    elsif( @files > scalar keys %last ) {
        my %temp;
        @temp{ @files } = ();
        delete @temp{ keys %last };
        print 'These files where created: ';
        print for keys %temp;
            print'';
    }
    else {
        print "A non-deletion or creation change occured";
    }
    undef %last;
    @last{ @files } = ();
}
__END__
P:\test>changenotify
Nothing changed
Nothing changed

Something changed
These files where created:
p:\test/fred

Nothing changed
Nothing changed

Something changed
These files where deleted:
p:\test/fred

Nothing changed
Nothing changed
Nothing changed
Nothing changed
[download]

You'll need control-break rather than ^C to interupt this script.

To extending this to monitor the whole subtree, change the 0 in the new() call to 1, though you'll need some extra work to find out what changed where.

I'm not aware of a similar mechanism under *nix.