title: Replace characters (unique then wildcard value) in a string with other characters
body: <p>I have an NSString, let's say "H,L,K,P" how can I detect a specific character than then a wild-car character... for example, checking for ",*" would return ",L" ",K" and ",P" because they all have the specific "," and then they all have a character after them. Then I want to replace that string with itself plus a "period" appended to it.</p>
  
  <p>So "H,L,K,P" would become "H,L.,K.,P."</p>