problema com o link de form action="link.php"

<form action="processar_evento.php?filename=$filename">
<header class="main-header clearfix">
  <div class="container">
        <h1 class="page-title pull-left"> <input type="text" name="titulo" value="<?php echo $reg['nome']; ?>" </h1>
  </div>
</header>

<section class="content-area bg1">
  <div class="container">
        <div class="row">
          <div class="col-md-8">
                <img src="images/eventos/<?php echo $lol ; ?>" alt=" ">
          </div>
          <div class="col-md-4">
                <dl>
                  <dt>Data</dt>
                  <dd><input type="text" name="data" value="<?php echo $reg['data'];?>" </dd>
                  <dt>Descrição do evento</dt>
<textarea  name="descr" cols="20" rows="5" > <?php echo $reg['descr']; ?>  </textarea>
<br>
<input type="submit" >
</form>