Is there a way of handling collective nouns

[danielneal]

e.g.

Group of plants => groups of plants
Box of eggs => boxes of eggs

It doesn't look possible to add via the standard add-rule! because that needs a static replacement, whereas the logic is something along the lines of #"(?i)(.+) of (.+)" => (fn [[$1 $2]] (str (plural $1) " of " $2)).

Any ideas? For now I can just add exact matches.