The following code: (EVAL-WHEN (EVAL COMPILE) (LOAD'LIBLSP/;IOTA)) (DEFUN SMART-PROBEF (FILE) (AND (ERRSET (IOTA ((STREAM FILE '(IN NODEFAULT))) T) NIL) T)) when called on a non-existent file -- eg, (SMART-PROBEF '((DSK FOO) BAR BAZ)