title: mod_rewrite: replace underscores with dashes
body: <p>I'm revealing my embarrassing ignorance of REGEX-fu here, but: I currently have a website where a load of the articles' URLs are written as "article_name", whilst the newer ones are written as "article-name".</p>
  
  <p>I want to move all of them to using dashes, so is there a regular expression I could use to rewrite the older URLs to their newer equivalents?</p>
  
  <p>Thanking you in advance!</p>