purge-hash deletes all elements from <hash> that was created with new-hash.
After purge-hash, you can use it without calling new-hash again. Note however, that "average-reads" statistics (see get-hash) is not reset - it keeps being computed and remains for the life of the hash.
Examples
Create a hash, put some data in it and then delete the data:
new-hash h
write-hash h key"mykey" value"myvalue" purge-hash h
