Apparently construct 3 for some reason does not digest the "str" operator well???
No, str expression works as expected. You need to read again all the comments in this post.
"tag1"&"tag2"="tag1tag2" <- a single tag
"tag1"&" tag2"="tag1 tag2" <- two tags, separated by space
"tag1"&" "&"tag2"="tag1 tag2" <- also two tags, separated by space