What's the safest way to iterate through the keys of a Perl hash?

Question

If I have a Perl hash with a bunch of (key, value) pairs, what is the preferred method of iterating through all the keys? I have heard that using each may in s

Answer 1

A few miscellaneous thoughts on this topic:

1. There is nothing unsafe about any of the hash iterators themselves. What is unsafe is modifying the keys of a hash while you're iterating over it. (It's perfectly safe to modify the values.) The only potential side-effect I can think of is that values returns aliases which means that modifying them will modify the contents of the hash. This is by design but may not be what you want in some circumstances.
2. John's accepted answer is good with one exception: the documentation is clear that it is not safe to add keys while iterating over a hash. It may work for some data sets but will fail for others depending on the hash order.
3. As already noted, it is safe to delete the last key returned by each. This is not true for keys as each is an iterator while keys returns a list.