If you are using a shared libperl, see the warnings about multiple
versions of perl under L<Building a shared Perl library>.
+Note that a perl built with -DDEBUGGING will be bigger and will run more
+slowly than a standard perl.
+
+=head2 DTrace support
+
+On platforms where DTrace is available, it may be enabled by
+using the -Dusedtrace option to Configure. DTrace probes are available for
+subroutine entry (sub-entry) and subroutine exit (sub-exit). Here's a
+simple D script that uses them:
+
+ perl$target:::sub-entry, perl$target:::sub-return {
+ printf("%s %s (%s:%d)\n", probename == "sub-entry" ? "->" : "<-",
+ copyinstr(arg0), copyinstr(arg1), arg2);
+ }
+
+
=head2 Extensions
Perl ships with a number of standard extensions. These are contained
at Perl startup.
+=item other environment variables
+
+Configure does not check for environment variables that can sometimes
+have a major influence on how perl is built or tested. For example,
+OBJECT_MODE on AIX determines the way the compiler and linker deal with
+their objects, but this is a variable that only influences build-time
+behaviour, and should not affect the perl scripts that are eventually
+executed by the perl binary. Other variables, like PERL_UNICODE,
+PERL5LIB, and PERL5OPT will influence the behaviour of the test suite.
+So if you are getting strange test failures, you may want to try
+retesting with the various PERL variables unset.
+
=item varargs
If you get varargs problems with gcc, be sure that gcc is installed