DISCLOSURE: I realize that this is not a timely reply, but since this post comes up in Google searches for "remove duplicate characters in a SAS string", I have decided to inform readers who stumble upon this post through their search about the following new development:
I recently published a blog post Removing repeated characters in SAS strings in which I create a new user-defined function UNDUPC that removes duplicate characters from SAS strings effectively expanding functionality of the COMPBL function to all other characters.
... View more