use v5.12.0;
use warnings;
use Test::More;
use Data::Dump;


sub orig_data {
    return
      [
       {
        foo => {
                browser => "firefox",
                contact => [{ email => "foo\@example.org" }, { phone => 2125551212 }],
                lang    => "en",
               },
       },
       {
        bar => {
                browser => "lynx",
                contact => [{ email => "bar\@example.com" }, { phone => 9125551212 }],
                lang    => "fr",
               },
       },
      ];
}

my $data = orig_data();

my @emails;

# ------ short version
@emails =
  map { $_->{email} // () }
  map { @{ $_->{contact} // [] } }
  map { $_->{bar} // () }
  @$data;

is_deeply(\@emails, ["bar\@example.com"], "result ok");
is_deeply($data, orig_data(), "no autovivification");


# ------ long symmetrical version
@emails =
  map { $_->{email} // () }
  map { @$_ }
  map { $_->{contact} // () }
  my @users =                            # only necessary to check uniqueness
  map { $_->{bar} // () }
  map { @$_ }
  $data;

is_deeply(\@emails, ["bar\@example.com"], "result ok");
is_deeply($data, orig_data(), "no autovivification");



# --------- this would vivify new elements
# map { $_->{bar}{contact} // () }
#   map { @$_ }
#   $data;

# is_deeply($data, orig_data ,"no autovivification");

done_testing;