When called in list context, returns a 2-element list consisting of the key and value for the next element of a hash, or the index and value for the next element of an array, so that you can iterate over it. When called in scalar context, returns only the key (not the value) in a hash, or the index in an array.
Hash entries are returned in an apparently random order. The actual random
order is subject to change in future versions of Perl, but it is
guaranteed to be in the same order as either the keys or values
function would produce on the same (unmodified) hash. Since Perl
5.8.2 the ordering can be different even between different runs of Perl
for security reasons (see Algorithmic Complexity Attacks in perlsec).
After each has returned all entries from the hash or array, the next
call to each returns the empty list in list context and undef in
scalar context. The next call following that one restarts iteration. Each
hash or array has its own internal iterator, accessed by each, keys,
and values. The iterator is implicitly reset when each has reached
the end as just described; it can be explicitly reset by calling keys or
values on the hash or array. If you add or delete a hash's elements
while iterating over it, entries may be skipped or duplicated--so don't do
that. Exception: It is always safe to delete the item most recently
returned by each(), so the following code works properly:
This prints out your environment like the printenv(1) program, but in a different order: