Tiger upgrades Perl from 5.8.1 to the latest 5.8.6. Sadly, it doesn't include the header files and various other goodies that 5.8.1 did. This means that installing some modules can be very tough (namely String::CRC32, in my case) as it can't use the various EXTERN.h and CONFIG.h files in the XS compiles. Here's how to resolve the issue..

To get around this, download Perl 5.8.6 from http://www.perl.com/CPAN/src/stable.tar.gz, tar xzvf it, build it, then..

sudo mv /usr/bin/perl /usr/bin/perl~

ln -s /usr/local/bin/perl /usr/bin/perl

and you're good to go. CPAN may flake out on you though. If so, try perl -e "use CPAN; shell();" This works for me even when the usual cpan or perl -MCPAN -e"shell" does not.