Perl Study Notes No. 6

1. Since each Hash has a private iterator (iterator), the loop using each can be nested, because different hash
There are different iterator. Although this is just a footer, we should also tell you that you can use keys or values
Function, reset the iterator (iterator). If the new list is added to this hash, or each
When the function iterates to the last element, it also resets the iterator. If a new key/value is added to the iteration
Yes, it is usually a bad idea. It won't reset the iterator, but it is likely to confuse you and maintenance personnel.

2. The exists function checks whether a key exists in the hash, for example, exists $ hash {key}

3. The delete function deletes a given key (including its corresponding value) from the hash. If this key does not exist, nothing is done. No warning or error message is provided.

4. Use () instead of {} for hash assignment {}! When you enter the value of the specified key, use {}