the additional information automatically disappears when the original
data is no longer in use and gets garbage collected. In a weak key hash,
the hash entry for that key disappears as soon as the key is no longer
-referneced from anywhere else. For weak value hashes, the same happens
+referenced from anywhere else. For weak value hashes, the same happens
as soon as the value is no longer in use. Entries in a doubly weak hash
disappear when either the key or the value are not used anywhere else
anymore.