my $followers = $data->{followersperdate}; ## just copy the reference to the interesting part of the hash

** OR **

my %followers = %{ $data->{followersperdate} }; ## dereference the interesting bit

##</code><code>##

my @sorted_keys = 
  sort 
    { $data->{ followersperdate }->{ $b } 
      <=> 
    $data->{ followersperdate }->{ $a } } ## hi to lo on values
      keys %{ $data->{ followersperdate } }; ## again dereferencing as above