my $self = {};                 # is a hash ref
$self->{foo};                  # element foo of that hash
$self->{foo} = ['bar', 'baz']; # assign an arrayref to that element
@{$self->{foo}};               # element of the hash, dereferenced as an array.
@{$self->{foo}} = (1,2);       # assign (1, 2) to the array.
push @{$self->{foo}}, (3);     # array now contains 1,2,3