my %h = (
  fruits => {
    p => [ 'peach' ],
    g => [ 'grapes' ],
  },
  birds => {
    p => [ 'parrot' ],
    c => [ 'crow' ],
  }
);

##</code><code>##

@all_p_fruits = @{$h{fruits}->{p}};

##</code><code>##

push @{$h{fruits}->{p}}, 'peach_yellow';