Sounds like you need to work with hash and array slices. But you'll also have to decide what you mean by "first key", "second key", etc. Hash keys don't have a meaningful ordering of their own. You have to impose the order on them from the outside:

# put keys in ascending asciibetical order
my @aKeys = sort keys %hSomeHash;

#put keys in descending asciibetical order
@aKeys = sort { $b cmp $a } keys %hSomeHash;

# @var{keys} is a hash slice
# @var[number range] is an array slice

@hSomeHash{@aKeys[0..4]};  #values for first 5 sorted keys
@hSomeHash{@aKeys[5..9]};  #values for next 5 sorted keys

# or to create a hash from the a subset of keys
my %hash0_4 = map { $_ => $hSomeHash{$_} } @aKeys[0..4];
my %hash5_9 = map { $_ => $hSomeHash{$_} } @aKeys[5..9];
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For more about array and hash slices, see perldata. You may also find sort and map helpful.

Best, beth

Update: added sample code for using array slice to create a subset hash