Copy the top value from the return stack to the data stack.
Forth uses two stacks, the data stack and the return stack. Most operations occur on the data stack. The return stack can be crucial when reaching below the top two data stack elements, or to put aside values. In traditional Forth, the return stack does, double duty, being used to track the return address of the current caller of a word. As such, it is important to balance what you push and pop to the return stack within each scope. The current Haiku Forth implement does not use the return stack for flow control, however, this behavior may change in future versions.
NOTE: In Haiku Forth (unlike Traditional Forth), all stack cells and memory locations are floating point numbers.