$batch_dir = "batch/";
$log_dir = "batchlog/";

while (1) {
    opendir( D, $batch_dir ) or die;
    print "checking $batch_dir for files\n";
    @batchfiles = grep { !/^\./ } readdir(D);

    unless (@batchfiles) {
        print "Done: no more files to process\n";
        exit;
    }

    # batchfiles contains all files at 
    # most recent readdir() 
    foreach $file (@batchfiles) {
        open( F, "$batch_dir$file" ) or die "$!";
        while (<F>) {
            do_stuff_with($_);
            # actual processing omitted
        }
        close(F);
        rename("$batch_dir$file","$log_dir$file") || die "$!";
        print "finished $file\n";
    }
}