++ to you. That's the way to go.

I like let handles close automatically on block exit (where feasible) and since this snippet fits naturally in a sub, I'd do this:

sub files_in_dir
{
    my $dir = shift || '.';
    opendir my $dh, $dir or croak "opendir '$dir' - $!";
    grep { -f } readdir $dh;
}
[download]

It produces the number of files if called in scalar context and the list of filenames if called in list context.