simply returns `M`: `((\x x) M) ~~> M`.
> `(\x (x x))` duplicates its argument (applies it to itself):
-`((\x (x x)) M) ~~> (M M)` <!-- **M** or ω; W is \uv.uvv -->
+`((\x (x x)) M) ~~> (M M)` <!-- **M** or ω; W is \uv.uvv, L is \uv.u(vv) -->
> `(\x (\y (y x)))` reorders its two arguments:
`(((\x (\y (y x))) M) N) ~~> (N M)` <!-- **T**; C is \uvx.uxv -->