(a | b)
a; g
((a | (b; g)) | e)
(((a | b); g) | c)
((a | b) | c); (g | h)
a; (b | (c; (d; (e | (f; g)))))
(a | b); (c | d)
a; ((b | c) | d)
(((a | (b; c)) | d) | e) | pure
((a | b); (c | d)) | e
(a | b) | pure
a | (b; c)