Notation for sets in n3

Recently, it was decided that Cwm should have support for sets.

This leads to the question, what delimeter should a set have in n3? The 
problem is n3 already use every ascii delimeter I can think of.
    (...) is taken for lists
    {...} is taken for formulae
    [...] is taken for anonymous nodes
    <...> is taken for resources

My father suggested «...», but being as that cannot be typed on a 
standard keyboard, is unlikely to be useful.

My personal opinion is something like {|...|} would be best. Something 
like $(...) might also work. It seems no matter what we do, readability 
is compromised.

Yosi