First thing - regex101.com is your friend. You can pop over there and check out whether your regular expression will match any particular incoming data.
In this case, if you want this file to be excluded...
/export/logs/vol-ext-test-ind-UPC-input.log
...and if it's ANY log file with UPC somewhere in the file name, then you need a wildcard between UPC and .log to pick up all those letters in -input. That could be like this...
blacklist = UPC.*\.log$
Now, a . matches EVERYTHING, so you will notice that I escaped it with a slash like this \., to tell the system that I meant to match only a period character, not anything else.
In general, I tend to be paranoid, so I'd also want to make sure that slashes between UPC and .log were NOT matched. This would only be relevant if the particular stanza had some directory wildcarding that could potentially come up with a directory that had UPC in the name. That would look something like this.
blacklist = UPC[^\/]*\.log$
