my $entry = { firstname => 'Ola', lastname => 'Nordmann' }; 
my $staff = {};

my $id = 123;
$staff->{$id} = $entry;

printf(
  "%d: %s, %s\n", 
  $id, 
  $staff->{$id}->{'lastname'}, 
  $staff->{$id}->{'firstname'}
);