Is there a way to check for duplicates when adding a Structured Information?

[José Oliver-Didier]

I was experimenting with the LocationCreatedLocationID struct tags and entered the same command twice.

exiftool -LocationCreatedLocationID+="A"
exiftool -LocationCreatedLocationID+="A"

Upon examining the XMP I discovered that the entry "A" was added twice (duplicated). Is there a way to avoid this from happening? A flag which checks to see if the information already exists and does not add it again?

[Phil Harvey]

Yes.  See the 3rd last example in FAQ 17

- Phil