macro foo
  %w(four (five) six) # okay, second element is "(five)"
end

# okay, second `(` does not start a nested region
# errors on macro expansion instead
macro foo
  %w(four (five) %w(six)
end

# error, `w` inside `two` starts a nested region but only one `)` found
macro foo
  %w(one two three)
end

# okay, every `w` is "matched" by a closing `)`
# errors on expansion
macro foo
  %w(www))))
end