sub Traverse {
    my $dir = shift;
    opendir my $dh, $dir or return 0;
    for my $file ( grep !/^\.\.?$/, readdir $dh ) {
        my $path = "$dir/$file";
        if ( -d $path ) {
            Traverse( $path, @_ );
        }
        elsif ( -f $path )  {
            ProcessFile( $path, @_ );
        }
        else {
            warn "$path not -d or -f\n";
        }
    }
    closedir $dh;
}