fitlers with blocks

[ralyodio]

I have a block I'm override in layout template:

<% block('title', owner + "'s list" %> which will produce "Bill's list"

I want to use a filter here though that I created called 'possessive' which will add the apostrophe s properly (ie: Wes would become Wes' instead of Wes's)

I can echo it find, but how would I use a filter with a block value?

<%=: owner | possessive %>