$ su -                               # Become root.
$ chmod 000 /opt/perl/lib/site_perl  # As root.
$ ^D
# Normal user again. No LWP and a whole lot of dependencies available.
$ rm -rf ~/cpan/build/*              # Clear cache
$ perl -MLWP -e1
Can't locate LWP.pm in @INC (@INC contains: ...)
$ perl -MCPAN -e'test "LWP"'
...
Prepending /home/anonmonk/cpan/build/Compress-Zlib-1.34/blib/arch /home/anonmonk/cpan/build/Compress-Zlib-1.34/blib/lib /home/anonmonk/cpan/build/HTML-Tagset-3.04/blib/arch /home/anonmonk/cpan/build/HTML-Tagset-3.04/blib/lib /home/anonmonk/cpan/build/URI-1.35/blib/arch /home/anonmonk/cpan/build/URI-1.35/blib/lib /home/anonmonk/cpan/build/HTML-Parser-3.45/blib/arch /home/anonmonk/cpan/build/HTML-Parser-3.45/blib/lib to PERL5LIB.
...
All tests successful, 4 tests skipped.
# Note, no installation. No attempts to installation either.
$ perl -MLWP -e1
Can't locate LWP.pm in @INC (@INC contains: ...)
$ perl -MURI -e1  # One of the dependencies.
Can't locate URI.pm in @INC (@INC contains: ...)
$ ls ~/cpan/build
Compress-Zlib-1.34  HTML-Tagset-3.04  libwww-perl-5.803
HTML-Parser-3.45    URI-1.35
$ su -
$ chmod 755 /opt/perl/lib/site_perl
$ ^D
$ perl -MLWP -e1
$