It's fun to answer questions that could be easily answered with a single invocation, but here goes: coercing a set ($set.Set) is a no-op. my $set-of-sets = set

It's fun to answer questions that could be easily answered with a single invocation, but here goes: coercing a set ($set.Set) is a no-op. my $set-of-sets = set $set; The above will create a new set with $set as its only member.