$ perldoc -f each
  each HASH
    Entries are returned in an apparently random order. [...] Since
    Perl 5.8.1 the ordering is different even between different
    runs of Perl for security reasons (see "Algorithmic Complexity
    Attacks" in perlsec).

##</code><code>##

$ PERL_HASH_SEED_DEBUG=1 perl -e 'my %a=0..299; print $_ for each %a' | md5sum
HASH_SEED = 3379561142
b6d67a24906e8a8541291882f81d31ca  -
$ PERL_HASH_SEED_DEBUG=1 perl -e 'my %a=0..299; print $_ for each %a' | md5sum
HASH_SEED = 4068799219
b6d67a24906e8a8541291882f81d31ca  -

##</code><code>##

$ PERL_HASH_SEED_DEBUG=1 perl -e 'my %a=0..299; print $_ for keys %a' | md5sum
HASH_SEED = 1151419008
dd56233cf84603df0d47d272da1af003  -
$ PERL_HASH_SEED_DEBUG=1 perl -e 'my %a=0..299; print $_ for keys %a' | md5sum
HASH_SEED = 2731377116
dd56233cf84603df0d47d272da1af003  -

$ PERL_HASH_SEED_DEBUG=1 perl -e 'my %a=0..299; print $_ for values %a' | md5sum
HASH_SEED = 1861095523
c1a75ab8e3bf1ff6c07b01025a1219e9  -
$ PERL_HASH_SEED_DEBUG=1 perl -e 'my %a=0..299; print $_ for values %a' | md5sum
HASH_SEED = 788024661
c1a75ab8e3bf1ff6c07b01025a1219e9  -

##</code><code>##

$ echo $RANDOM
8035
$ echo $RANDOM
797
$ PERL_HASH_SEED=$RANDOM PERL_HASH_SEED_DEBUG=1 perl -e 'my %a=0..299; print $_ for values %a' | md5sum
HASH_SEED = 26815
c1a75ab8e3bf1ff6c07b01025a1219e9  -
$ PERL_HASH_SEED=$RANDOM PERL_HASH_SEED_DEBUG=1 perl -e 'my %a=0..299; print $_ for values %a' | md5sum
HASH_SEED = 30449
c1a75ab8e3bf1ff6c07b01025a1219e9  -