title: Add tag to bioperl DB::SAM/BAM
body: <p>I have a bam file and use bioperl (Bio::DB::Sam) to work with it.
  Now i wanted to ask if there is any possibility to add tags to alignments in this File?</p>
  
  <p>i use </p>
  
  <pre><code>    my $iterator     = $bam-&gt;features(-iterator =&gt; 1,
                                        -flags    =&gt; {M_UNMAPPED=&gt;0});
  
      while (my $align = $iterator-&gt;next_seq) { 
          ...
      }
  </code></pre>
  
  <p>to loop through the aligned reads. Now i  am searching vor anthing like </p>
  
  <pre><code>    $align-&gt;addTag(key=&gt;value)
  </code></pre>
  
  <p>bye</p>