Under non-debugging builds, I get this:
$ perl -D -e 'print "ok\n"'
Recompile perl with -DDEBUGGING to use -D switch (did you mean -d ?)
ok
It is a default warning (S), not a fatal error (F).
=item Recompile perl with B<-D>DEBUGGING to use B<-D> switch
-(F debugging) You can't use the B<-D> option unless the code to produce
+(S debugging) You can't use the B<-D> option unless the code to produce
the desired output is compiled into Perl, which entails some overhead,
which is why it's currently left out of your copy.