The regular expression:

  /\w+ing\b/

matches as follows:
 
NODE                   EXPLANATION
====                   ===========
  \w+                    word characters (a-z, A-Z, 0-9, _) (1 or
                         more times)
   ing                   'ing'
   \b                     the boundary between a word char (\w) and
                         something that is not a word char