A minor detail: The key order in Perl hashes was always arbitrary (as opposed to in the order the keys were added) but identical hashes had the keys returned (by keys(), values(), etc) in the same order before Perl 5.18 (released about a year ago) [1].

[1] https://metacpan.org/pod/release/RJBS/perl-5.18.0/pod/perlde...