Each hash has only one iterator used by all each on that hash. You must have something like this:

my %h = map { $_ => 1 } qw( a b c d );

while (my $k = each(%h)) {
   last;
}

while (my $k = each(%h)) {
   print("$k\n");            # a b d
}
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Data::Dumper causes the iterator to be reset. keys(%h) will do that too.

my %h = map { $_ => 1 } qw( a b c d );

while (my $k = each(%h)) {
   last;
}

keys(%h);
while (my $k = each(%h)) {
   print("$k\n");            # c a b d
}
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