DB<110> %hash = ("fred" => "flintstone", "dino" => undef, "barney" => "rubble", "betty" => "rubble");

  DB<111> use Data::Dumper

  DB<112> print Dumper \%hash
$VAR1 = {
          'barney' => 'rubble',
          'betty' => 'rubble',
          'dino' => undef,
          'fred' => 'flintstone'
        };