$

pops the first item off the stack

:

duplicates the first item on the stack

+

sums the top two items on the stack

*

subtracts the top two items on the stack

-

multiples the top two items on the stack

/

divides the top two items on the stack

!

negates the first item

.

prints the first item without a newline and pops it

.\

prints the first item with a newline and pops it

~

swaps the top two items on the stack

:@

copies an item from a given index to the top of the stack

+s

concats the top two items on the stack (meant for strings)

<>

reverses the top n elements on the stack

λ

undocumented