Scieneer Common Lisp 1.3.9 online documentation

*macroexpand-hook*[Variable]

The value of this variable must be a function that can take three arguments, a macro expander function, the macro form to be expanded, and the lexical environment to expand in. The function should return the expanded form. This function is called by macroexpand-1 whenever a runtime expansion is needed. Initially this is set to funcall.