Store the order you want in an array.

$ perl -Mstrict -Mwarnings -E '
my %people;
$people{ Fred }->{ age } = 37;
$people{ Fred }->{ sex } = q{male};
$people{ Fred }->{ occ } = q{plumber};
$people{ Mary }->{ age } = 41;
$people{ Mary }->{ sex } = q{female};
$people{ Mary }->{ occ } = q{barmaid};

my @order = qw{ age sex occ };
foreach my $person ( keys %people )
{
    say qq{$person:};
    foreach my $attr ( @order )
    {
        say qq{     $attr: $people{ $person }->{ $attr }};
    }
}'
Mary:
     age: 41
     sex: female
     occ: barmaid
Fred:
     age: 37
     sex: male
     occ: plumber
$
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I hope this is helpful.