pleft.hello
<defer>
eleft.hello
eleft.return
<defer>
rleft.hello
rleft.return
pright.hello
<defer>
eright.hello
eright.return
<defer>
rright.hello
rright.return
eleft.world
rleft.world
<defer>
rleft.hello
rleft.return
rright.world
pright.return
rleft.world
pleft.return
