am getting this error: cannot encode reference to scalar 'SCALAR(0x55c89ffbc4f0)' unless the scalar is 0 or 1

my $dbh = DBI->connect("DBI:mysql:$dbname:$host", $usr, $pwd, {
                                  RaiseError => 1,
                                  }) or die $DBI::errstr;

my $sth = $dbh->prepare("SELECT titles FROM tbl_1");
$sth->execute();
my $Data = $sth->fetchall_arrayref();
my $output;

foreach my $Data (@$Data) {
    
my ($title) = @$Data; 

$output{items} ||= [];
push @{$output{items}}, {title => $title};
}

my $encoded = encode_json \$output;

print $Cgi->header( -type => 'application/json' ),$encoded;
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