$VAR1 = {
     'host' => {
           'jimmy.foo.com' => {
                      'hardware' => ['eht0', 'eht1'],
                      'duty' => 'web'
           },
      },
};

##</code><code>##

my $hosts = $data->{'host'};
foreach my $host ( keys %$hosts ) {
    my $duties = $hosts->{$host}->{'duty'};
    print "$host : $_\n"
      foreach ( UNIVERSAL::isa( $duties, 'ARRAY' )
        ? @$duties
        : $duties );
}