Help for this page
DB<166> %hash = (Canberra => { 12 => 1}, Canberra => { 18 => 1} ) => ("Canberra", { 18 => 1 })
DB<178> sub join_deep { my %hash; ... DB<179> %h =join_deep (Canberra => { 12 => 1}, Canberra => { 18 => 1 +} ) => ("Canberra", { 12 => 1, 18 => 1 })