+For information on compilers on older versions of AIX, see L<Compiling
+Perl 5 on older AIX versions up to 4.3.3>.
+
+When compiling Perl, you must use an ANSI C compiler. AIX does not ship
+an ANSI compliant C compiler with AIX by default, but binary builds of
+gcc for AIX are widely available. A version of gcc is also included in
+the AIX Toolbox which is shipped with AIX.
+
+=head2 Supported Compilers
+
+Currently all versions of IBM's "xlc", "xlc_r", "cc", "cc_r" or
+"vac" ANSI/C compiler will work for building Perl if that compiler
+works on your system.
+
+If you plan to link Perl to any module that requires thread-support,
+like DBD::Oracle, it is better to use the _r version of the compiler.
+This will not build a threaded Perl, but a thread-enabled Perl. See
+also L<Threaded Perl> later on.
+
+As of writing (2010-09) only the I<IBM XL C for AIX> or I<IBM XL C/C++
+for AIX> compiler is supported by IBM on AIX 5L/6.1/7.1.
+
+The following compiler versions are currently supported by IBM:
+
+ IBM XL C and IBM XL C/C++ V8, V9, V10, V11
+
+The XL C for AIX is integrated in the XL C/C++ for AIX compiler and
+therefore also supported.
+
+If you choose XL C/C++ V9 you need APAR IZ35785 installed
+otherwise the integrated SDBM_File do not compile correctly due
+to an optimization bug. You can circumvent this problem by
+adding -qipa to the optimization flags (-Doptimize='-O -qipa').
+The PTF for APAR IZ35785 which solves this problem is available
+from IBM (April 2009 PTF for XL C/C++ Enterprise Edition for AIX, V9.0).
+
+If you choose XL C/C++ V11 you need the April 2010 PTF (or newer)
+installed otherwise you will not get a working Perl version.
+
+Perl can be compiled with either IBM's ANSI C compiler or with gcc.
+The former is recommended, as not only it can compile Perl with no
+difficulty, but also can take advantage of features listed later
+that require the use of IBM compiler-specific command-line flags.
+
+If you decide to use gcc, make sure your installation is recent and
+complete, and be sure to read the Perl INSTALL file for more gcc-specific
+details. Please report any hoops you had to jump through to the
+development team.
+
+=head2 Incompatibility with AIX Toolbox lib gdbm
+
+If the AIX Toolbox version of lib gdbm < 1.8.3-5 is installed on your
+system then Perl will not work. This library contains the header files
+/opt/freeware/include/gdbm/dbm.h|ndbm.h which conflict with the AIX
+system versions. The lib gdbm will be automatically removed from the
+wanted libraries if the presence of one of these two header files is
+detected. If you want to build Perl with GDBM support then please install
+at least gdbm-devel-1.8.3-5 (or higher).
+
+=head2 Perl 5 was successfully compiled and tested on:
+
+ Perl | AIX Level | Compiler Level | w th | w/o th
+ -------+---------------------+-------------------------+------+-------
+ 5.12.2 |5.1 TL9 32 bit | XL C/C++ V7 | OK | OK
+ 5.12.2 |5.1 TL9 64 bit | XL C/C++ V7 | OK | OK
+ 5.12.2 |5.2 TL10 SP8 32 bit | XL C/C++ V8 | OK | OK
+ 5.12.2 |5.2 TL10 SP8 32 bit | gcc 3.2.2 | OK | OK
+ 5.12.2 |5.2 TL10 SP8 64 bit | XL C/C++ V8 | OK | OK
+ 5.12.2 |5.3 TL8 SP8 32 bit | XL C/C++ V9 + IZ35785 | OK | OK
+ 5.12.2 |5.3 TL8 SP8 32 bit | gcc 4.2.4 | OK | OK
+ 5.12.2 |5.3 TL8 SP8 64 bit | XL C/C++ V9 + IZ35785 | OK | OK
+ 5.12.2 |5.3 TL10 SP3 32 bit | XL C/C++ V11 + Apr 2010 | OK | OK
+ 5.12.2 |5.3 TL10 SP3 64 bit | XL C/C++ V11 + Apr 2010 | OK | OK
+ 5.12.2 |6.1 TL1 SP7 32 bit | XL C/C++ V10 | OK | OK
+ 5.12.2 |6.1 TL1 SP7 64 bit | XL C/C++ V10 | OK | OK
+ 5.13 |7.1 TL0 SP1 32 bit | XL C/C++ V11 + Jul 2010 | OK | OK
+ 5.13 |7.1 TL0 SP1 64 bit | XL C/C++ V11 + Jul 2010 | OK | OK
+
+ w th = with thread support
+ w/o th = without thread support
+ OK = tested
+
+Successfully tested means that all "make test" runs finish with a
+result of 100% OK. All tests were conducted with -Duseshrplib set.
+
+All tests were conducted on the oldest supported AIX technology level
+with the latest support package applied. If the tested AIX version is
+out of support (AIX 4.3.3, 5.1, 5.2) then the last available support
+level was used.
+
+=head2 Building Dynamic Extensions on AIX
+
+Starting from Perl 5.7.2 (and consequently 5.8.x / 5.10.x / 5.12.x)
+and AIX 4.3 or newer Perl uses the AIX native dynamic loading interface
+in the so called runtime linking mode instead of the emulated interface
+that was used in Perl releases 5.6.1 and earlier or, for AIX releases
+4.2 and earlier. This change does break backward compatibility with
+compiled modules from earlier Perl releases. The change was made to make
+Perl more compliant with other applications like Apache/mod_perl which are
+using the AIX native interface. This change also enables the use of
+C++ code with static constructors and destructors in Perl extensions,
+which was not possible using the emulated interface.
+
+It is highly recommended to use the new interface.
+
+=head2 Using Large Files with Perl
+
+Should yield no problems.
+
+=head2 Threaded Perl
+
+Should yield no problems with AIX 5.1 / 5.2 / 5.3 / 6.1 / 7.1.
+
+IBM uses the AIX system Perl (V5.6.0 on AIX 5.1 and V5.8.2 on
+AIX 5.2 / 5.3 and 6.1; V5.8.8 on AIX 5.3 TL11 and AIX 6.1 TL4; V5.10.1
+on AIX 7.1) for some AIX system scripts. If you switch the links in
+/usr/bin from the AIX system Perl (/usr/opt/perl5) to the newly build
+Perl then you get the same features as with the IBM AIX system Perl if
+the threaded options are used.
+
+The threaded Perl build works also on AIX 5.1 but the IBM Perl
+build (Perl v5.6.0) is not threaded on AIX 5.1.
+
+Perl 5.12 an newer is not compatible with the IBM fileset perl.libext.
+
+=head2 64-bit Perl
+
+If your AIX system is installed with 64-bit support, you can expect 64-bit
+configurations to work. If you want to use 64-bit Perl on AIX 6.1
+you need an APAR for a libc.a bug which affects (n)dbm_XXX functions.
+The APAR number for this problem is IZ39077.
+
+If you need more memory (larger data segment) for your Perl programs you
+can set:
+
+ /etc/security/limits
+ default: (or your user)
+ data = -1 (default is 262144 * 512 byte)
+
+With the default setting the size is limited to 128MB.
+The -1 removes this limit. If the "make test" fails please change
+your /etc/security/limits as stated above.
+
+=head2 Recommended Options AIX 5.1/5.2/5.3/6.1 and 7.1 (threaded/32-bit)
+
+With the following options you get a threaded Perl version which
+passes all make tests in threaded 32-bit mode, which is the default
+configuration for the Perl builds that AIX ships with.
+
+ rm config.sh
+ ./Configure \
+ -d \
+ -Dcc=cc_r \
+ -Duseshrplib \
+ -Dusethreads \
+ -Dprefix=/usr/opt/perl5_32
+
+The -Dprefix option will install Perl in a directory parallel to the
+IBM AIX system Perl installation.
+
+=head2 Recommended Options AIX 5.1/5.2/5.3/6.1 and 7.1 (32-bit)
+
+With the following options you get a Perl version which passes
+all make tests in 32-bit mode.
+
+ rm config.sh
+ ./Configure \
+ -d \
+ -Dcc=cc_r \
+ -Duseshrplib \
+ -Dprefix=/usr/opt/perl5_32
+
+The -Dprefix option will install Perl in a directory parallel to the
+IBM AIX system Perl installation.
+
+=head2 Recommended Options AIX 5.1/5.2/5.3/6.1 and 7.1 (threaded/64-bit)
+
+With the following options you get a threaded Perl version which
+passes all make tests in 64-bit mode.
+
+ export OBJECT_MODE=64 / setenv OBJECT_MODE 64 (depending on your shell)
+
+ rm config.sh
+ ./Configure \
+ -d \
+ -Dcc=cc_r \
+ -Duseshrplib \
+ -Dusethreads \
+ -Duse64bitall \
+ -Dprefix=/usr/opt/perl5_64
+
+=head2 Recommended Options AIX 5.1/5.2/5.3/6.1 and 7.1 (64-bit)
+
+With the following options you get a Perl version which passes all
+make tests in 64-bit mode.
+
+ export OBJECT_MODE=64 / setenv OBJECT_MODE 64 (depending on your shell)
+
+ rm config.sh
+ ./Configure \
+ -d \
+ -Dcc=cc_r \
+ -Duseshrplib \
+ -Duse64bitall \
+ -Dprefix=/usr/opt/perl5_64
+
+The -Dprefix option will install Perl in a directory parallel to the
+IBM AIX system Perl installation.
+
+If you choose gcc to compile 64-bit Perl then you need to add the
+following option:
+
+ -Dcc='gcc -maix64'
+
+
+=head2 Compiling Perl 5 on AIX 7.1.0
+
+A regression in AIX 7 causes a failure in make test in Time::Piece during
+daylight savings time. APAR IV16514 provides the fix for this. A quick
+test to see if it's required, assuming it is currently daylight savings
+in Eastern Time, would be to run C< TZ=EST5 date +%Z >. This will come
+back with C<EST> normally, but nothing if you have the problem.
+
+
+=head2 Compiling Perl 5 on older AIX versions up to 4.3.3
+
+Due to the fact that AIX 4.3.3 reached end-of-service in December 31,
+2003 this information is provided as is. The Perl versions prior to
+Perl 5.8.9 could be compiled on AIX up to 4.3.3 with the following
+settings (your mileage may vary):
+