title: expression + variable value + normal text in plot maintitle
body: <p>i want to achieve an title in R plot as the following:</p>
  
  <pre><code>title = "The significance level you entered is alpha = 0.05 which is often used."
  </code></pre>
  
  <p>In order to get this I split the whole text in little parts, so i finally can write</p>
  
  <pre><code>title = paste(part1,part2,part3,part4)
  </code></pre>
  
  <p>The parts are:</p>
  
  <pre><code>part1 = "The significance level you entered is"
  
  part2 = expression(alpha)
  
  part3 = object@attribute
  
  part4 = " which is often used."
  </code></pre>
  
  <p>So I'm not able to combine these parts to get my result. </p>
  
  <p>Either the symbol is shown correctly and the part 3 is printed as object@attribute (ant not his value) or the symbol is not shown and the value of the object is printed correctly. </p>
  
  <p>I used <code>?expression</code>and <code>?print</code>already, but didn't get it</p>
  
  <p>The examples provided in <code>?plotmath</code> didn't match my case either. </p>