my %foo;
my $bar = { key1 => "value 1", };
$foo{key2} = "value 2";
$$bar{key3} = "value 3";
$$bar{key4} = { key5 => "value 5", };
$$bar{key4}->{key6} = "value 6";
$$bar{key4}{key7} = "value 7"; # simpler syntax
use Data::Dumper;
print Dumper( \%foo, \$bar );