+ This is a problem in AFS for obvious reasons, since AFS does not use UNIX permissions. I happen to only need to install perl modules into lockers on which I am the owner; If you need to install things somewhere where the UNIX permission bits indicate you would not have access, you're out of luck as far as I can tell.
+
+ * Sharing a `local::lib` installation dir across multiple platforms is not recommended. While perl **does** include the architecture and sysname (e.g. `x86_64-linux-gnu-thread-multi/`) in the path when installing `.so` files for modules written in XS, it **does not** do the same for the version of Perl itself. So while you can share a single installation directory between 32- and 64-bit platforms, or between Linux and Solaris, all kinds of things will go wrong if you try to share it between a 32-bit perl 5.8 and a 32-bit perl 5.10 on the same platform.
+
+I work around this for BarnOwl by having completely separate perl module installs for every AFS sysname we support. This is painful to maintain, but I've found it to be the most reliable option.
+
+[filetest]: http://search.cpan.org/~dapm/perl-5.10.1/lib/filetest.pm
+
+
+## Cheat-sheet
+<a name="cheatsheet" />
+
+### Installing packages system-wide
+
+ $ env PERL_MM_USE_DEFAULT=1 cpan
+ # Answer 'yes' if CPAN asks to configure itself automatically
+ cpan> o conf make_install_make_command '/usr/bin/sudo /usr/bin/make'
+ cpan> o conf mbuild_install_build_command '/usr/bin/sudo ./Build'
+ cpan> o conf prerequisites_policy follow
+ cpan> o conf commit
+ cpan> install Some::Module
+
+### Installing packages into a directory
+ $ wget http://search.cpan.org/CPAN/authors/id/A/AP/APEIRON/local-lib-1.004009.tar.gz
+ $ tar xzf local-lib-1.004009.tar.gz
+ $ cd local-lib-1.004009/
+ $ perl Makefile.PL --bootstrap=/install/dir/
+ $ make && make install
+ $ eval $(perl -I/install/dir/lib/perl5/ -Mlocal::lib)
+ $ env PERL_MM_USE_DEFAULT=1 cpan
+ # Answer 'yes' if CPAN asks to configure itself automatically
+ cpan> o conf prerequisites_policy follow
+ cpan> o conf commit
+ cpan> install Some::Module