Search and Replace: want to remove value that matches another field

[einniv]

I'm curious how to accomplish something in the bulk edit search and replace. I was trying to do it earlier but ended up finding another way to accomplish what I wanted. I'd still like to know how to do it in case something similar comes up in the future.

I have a #kindlecollections tag-like text column that is populated by the kindle collections plugin. It has items I enter manually, which is usually genre and occasionally author, and items created by the plugin from the series field.

I'd like to pull the genre info out for a new custom series-like text column, #genre, but I don't want to pull out the bits that match the series field or author field for that book.

I went into bulk metadata edit and to the search and replace tab. I tried something like:
search field: #kindlecollections
search for: {series}
replace with: ??? have no idea what I'd replace it with but it doesn't seem to be finding what I'm looking for anyway.

That didn't work so I figured maybe a template as the search field could do it. It seemed like the template definition would probably do any actual work and the I'd just search on .* and put \1 in the new field. I couldn't get it to work though. Anyone want to help me take a crack at it? Like I said, it isn't critical anymore but I'm still curious how to do it.