 '<ins>$1</ins>')
  mdstr = mdstr.replace(/~~(\w.*?)~~/gm, '<del>$1</del>')
                
  // line break and paragraph => <br/> <p>                
  mdstr = mdstr.replace(/  \n/g, '\n<br/>').replace(/\n\s*\n/g, '\n<p>\n')
      
  // indent as code-block          
  mdstr = mdstr.replace(/^ {4,10}(.*)/gm, function(m,p) { return '<pre><code>' + md.formatTag(p) + '</code></pre>'} )
  mdstr = mdstr.replace(/^\t(.*)/gm, function(m,p) { return '<pre><code>' + md.formatTag(p) + '</code></pre>'} )
  mdstr = m