-- main.mcl --
$st1 = struct{
	a => 42,
	b => true,
	c => "pass1",
}

test [$st1->c || "default"] {}
test [$st1->missing || "pass2"] {}

$st2 = struct{
	a => 42,
	b => true,
	c => "pass3",
}

test [$st2->c] {}
#test [$st2->missing + "fail"] {} # this can't unify! (by design!)
-- OUTPUT --
Vertex: test[pass1]
Vertex: test[pass2]
Vertex: test[pass3]
