Append tag from single source file to extant XMP sidecar file

[redfishingboat]

OK I have spent an hour trying to RTFM and other forum posts and I am still stumped, so now I must ask here. Sorry if this is obvious

I am trying to copy the contents of the FilmMode tag from a Fuji RAF and append to the Subject tag in an already existing XMP sidecar, which already has some info.   I have this command which will replace the contents of the Subject tag.  I see many examples for appending that say to repeat the tag name, but I don't see how to combine the append operation with the copy from other field operation

exiftool -tagsfromfile 20211123_0063.RAF "-Subject<FilmMode" -ext xmp 20211123_0063.XMP

I think I have seen https://exiftool.org/metafiles.html for how to do something this for entire directories, but not sure how to apply it to a single file.

And I gather there is a way to use "%d%f" so that I don't need to include the full filename a second time, but I am not good at scripting, unfortunately. 

Thanks in advance if anyone knows how to do this.

Mick

[StarGeek]

See the last paragraph of FAQ #17.

exiftool -tagsfromfile 20211123_0063.RAF "-Subject+<FilmMode" -ext xmp 20211123_0063.XMP

[redfishingboat]

Thank you SG. Much appreciate -- sorry I did not check there earlier.