Perl插入数据库的字符问题，求大神帮忙，妹纸急求

根据结果集新增另一张表的记录，insert语句里有.，perl语法报错，求大神指教。
例子：

sub SetMassTaskData
{
my (@row, $sth, $rows);

my ($id, $content);
my $query_sql = "SELECT id,content FROM tableA WHERE  sendtime <= now()";
#print "query groupsend $query_sql\n";
$sth = $DB->prepare($query_sql);
$sth->execute();

while(@row = $sth->fetchrow_array())
{
    $id = $row[0];
    $content = $row[1];

    if($content ne '')
    {
        #status=2 is require to send
        $rows = $DB->do("insert into tableB(flag, content) values(1, $content)");
    }
    break;
}
$sth->finish();

}

因为$content的字符串总是带.的，执行总是报错，求解

$rows = $DB->do("insert into tableB(flag, content) values(1, '$content')");