or download this
open(INPUT,$file) or die ("Error opening '$file' for input: $!\n");
open(OUTPUT,">".$file) or die ("Error opening '$file' for output: $!\n
+");
...
}
close(INPUT) or die "Couldn't close '$file' after input: $!\n";
close(OUTPUT) or die "Couldn't close '$file' after output: $!\n";