...
  $count = $dbh->do("INSERT INTO  ques (...) VALUES (...)",
                    undef,
                    $usernamenow,
                    $txtque,
                    ...
           );
...

##</code><code>##

  $count = $dbh->do('INSERT INTO ques (...) VALUES (?,?,?,?,...)',
                    undef,
                    $usernamenow,
                    $txtque,
                    ...
           );