To enter two numbers in succession, separate them with spaces or newlines. These have no meaning as commands. Printing Commands p Prints the value on the top of the stack, without altering the stack. A newline is printed after the value. Prints the value on the top of the stack, popping it off, and does not print a newline after.
P Pops off the value on top of the stack.
If it it a string, it is simply printed without a trailing newline. This is a good command to use if you are lost or want to figure out what the effect of some command has been. The precision of the result is determined only by the values of the arguments, and is enough to be exact. Pops two values, subtracts the first one popped from the second one popped, and pushes the result. Pops two values, multiplies them, and pushes the result.