-behavior for that situation. Thus we set *DEBUG-IO* to send its
-output to *ERROR-OUTPUT*, and to raise an error if any input is
-requested from it; and we set *DEBUGGER-HOOK* to output a backtrace,
-then exit the process with a failure code.
+behavior for that situation. This is implemented by modifying special
+variables: we set *DEBUG-IO* to send its output to *ERROR-OUTPUT*, and
+to raise an error if any input is requested from it, and we set
+*DEBUGGER-HOOK* to output a backtrace, then exit the process with a
+failure code. Because it is implemented by modifying special variables,
+its effects persist in .core files created by SB-EXT:SAVE-LISP-AND-DIE.
+(If you want to undo its effects, see the SB-EXT:ENABLE-DEBUGGER
+command.)