exists(  $h->{'hello'})       # checks if hello exists.
scalar(@{$h->{'hello'}})      # The number of lists (2).
         $h->{'hello'}[1]     # The second list ([5,6,7,8]).
scalar(@{$h->{'hello'}[1]})   # The size of the second list (4).
         $h->{'hello'}[1][0]  # The first num of second list (5).