Last night, I dreamed I was cleaning up the garden, and there was a violently living green weed I was trying to pull up. It was growing like knotweed, except tall and leafy, and the more I struggled with it (with a machete!) the less good it did. I began to be rather afraid of it as I fought it, and I jumped out of the way and flinched back when a branch came crashing down.
On closer inspection I then discovered that the weed was implemented as an s-expression, so I merely (reverse)d it and it became nothing more than a little sprout in the ground I picked and threw away.