The SLIME scratch buffer, in contrib package
imitates Emacs’ usual
slime-scratch-file is set, it is used to back the scratch
buffer, making it persistent. The buffer is like any other Lisp
buffer, except for the command bound to C-j.
Evaluate the expression sexp before point and insert print value into the current buffer.
Create a *slime-scratch* buffer. In this buffer you can enter Lisp expressions and evaluate them with C-j, like in Emacs’s *scratch* buffer.