Mmmn, HN stripped out the half of the double asterisks, now I made it confusing myself... Too late to edit my comment above, but it needs to be like this: ** s

Mmmn, HN stripped out the half of the double asterisks, now I made it confusing myself... Too late to edit my comment above, but it needs to be like this: ** stands for exponentiation: so [expr {-2**2}] results in 4