use Data::Dumper;

my %h = (
  foo => 42,
  bar => {
    x => {
      u => 1,
      v => 2
    },
    y => 'blubb'
  }
);

print Dumper \%h;

hpush %h, 1, (
  baz => 23,
  bar => {
    x => {
      w => 3
    },
    z => 'blargh'
  }
);


print Dumper \%h;