Set:

$flags |= 1 << $bit_num;
[download]

Clear:

$flags &= ~( 1 << $bit_num );
[download]

Toggle:

$flags ^= 1 << $bit_num;
[download]

Read (returns a true value or a false value):

$flags & ( 1 << $bit_num )
[download]

---

It looks like you have constants that are already of the form 1 << $bit_num, so

$stats &= ~downLoading;   # No longer downloading.
[download]