Each of these is explained in further detail below.
+B<NOTE>: starting from the release 5.6.0 Perl will use a version
+scheme where even-numbered subreleases (like 5.6) are stable
+maintenance releases and odd-numbered subreleases (like 5.7) are
+unstable development releases. Development releases should not be
+used in production environments. Fixes and new features are first
+carefully tested in development releases and only if they prove
+themselves to be worthy will they be migrated to the maintenance
+releases.
+
The above commands will install Perl to /usr/local or /opt, depending
on the platform. If that's not okay with you, use
sh Configure -des
-For my Solaris system, I usually use
+Note: for development releases (odd subreleases, like 5.7, as opposed
+to maintenance releases which have even subreleases, like 5.6)
+if you want to use Configure -d, you will also need to supply -Dusedevel
+to Configure, because the default answer to the question "do you really
+want to Configure a development version?" is "no". The -Dusedevel
+skips that sanity check.
+
+For example for my Solaris system, I usually use
sh Configure -Dprefix=/opt/perl -Doptimize='-xpentium -xO4' -des
Eventually (by perl v5.6.0) this internal confusion ought to disappear,
and these options may disappear as well.
+=head2 64 bit support.
+
+If your platform does not have 64 bits natively, but can simulate them with
+compiler flags and/or C<long long> or C<int64_t>, you can build a perl that
+uses 64 bits.
+
+There are actually two modes of 64-bitness: the first one is achieved
+using Configure -Duse64bitint and the second one using Configure
+-Duse64bitall. The difference is that the first one is minimal and
+the second one maximal. The first works in more places than the second.
+
+The C<use64bitint> does only as much as is required to get 64-bit
+integers into Perl (this may mean, for example, using "long longs")
+while your memory may still be limited to 2 gigabytes (because your
+pointers could still be 32-bit). Note that the name C<64bitint> does
+not imply that your C compiler will be using 64-bit C<int>s (it might,
+but it doesn't have to): the C<use64bitint> means that you will be
+able to have 64 bits wide scalar values.
+
+The C<use64bitall> goes all the way by attempting to switch also
+integers (if it can), longs (and pointers) to being 64-bit. This may
+create an even more binary incompatible Perl than -Duse64bitint: the
+resulting executable may not run at all in a 32-bit box, or you may
+have to reboot/reconfigure/rebuild your operating system to be 64-bit
+aware.
+
+Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
+nor -Duse64bitall.
+
+ NOTE: 64-bit support is still experimental on most platforms.
+ Existing support only covers the LP64 data model. In particular, the
+ LLP64 data model is not yet supported. 64-bit libraries and system
+ APIs on many platforms have not stabilized--your mileage may vary.
+
+=head2 Long doubles
+
+In some systems you may be able to use long doubles to enhance the
+range and precision of your double precision floating point numbers
+(that is, Perl's numbers). Use Configure -Duselongdouble to enable
+this support (if it is available).
+
+=head2 "more bits"
+
+You can "Configure -Dusemorebits" to turn on both the 64-bit support
+and the long double support.
+
=head2 Selecting File IO mechanisms
Previous versions of perl used the standard IO mechanisms as defined in