Variable CUSTOM:*PRINT-UNREADABLE-ANSI*. The macro PRINT-UNREADABLE-OBJECT, when invoked without body forms, suppresses the trailing space if only the type is to be printed, and suppresses the leading space if only the identity is to be printed. This behaviour can be turned off set setting the variable CUSTOM:*PRINT-UNREADABLE-ANSI* to a non-NIL value: in this case, a trailing or leading space are output, as prescribed by [ANSI CL standard].