title: Regular expression to match unescaped special characters only
body: <p>I'm trying to come up with a regular expression that can match only characters not preceded by a special escape sequence in a string.</p>
  
  <p>For instance, in the string <code>Is ? stranded//?</code> , I want to be able to replace the <code>?</code> which hasn't been escaped with another string, so I can have this result : <code>**Is Dave stranded?**</code></p>
  
  <p>But for the life of me I have not been able to figure out a way. I have only come up with regular expressions that eat all the replaceable characters.</p>
  
  <p>How do you construct a regular expression that matches only characters not preceded by an escape sequence?</p>