Today I was installing a module within CPAN and I got systematically the same error ending as following:

[geshifilter-code] Catching error: "Undefined subroutine &Compress::Zlib::gzopen called at /System/Library/Perl/5.8.8/CPAN/Tarzip.pm line 122.\cJ" at /System/Library/Perl/5.8.8/CPAN.pm line 359 CPAN::shell() called at /usr/bin/cpan line 198 [/geshifilter-code]

After consulting my "Perl menthor" (hehe!), he asked me if I had installed the 2009-001 Mac OS X Security Update. Well it seems that this Update troubles the IO module.

Let me explain: each time you run an update with Software Update, it simply overrides your existing files. This is the main reason you shouldn't override the system Perl installation with a fresh one compiled from source, for instance.

So, getting back to our subject, let me explain how I solved that.

First of all, you have to download the IO module source:
[geshifilter-code language="bash"] nuno@mac ~ $ wget http://search.cpan.org/CPAN/authors/id/G/GB/GBARR/IO-1.2301.tar.gz [/geshifilter-code]
or using curl, as wget is not shipped with Mac OS X:
[geshifilter-code language="bash"] nuno@mac ~ $ curl -O http://search.cpan.org/CPAN/authors/id/G/GB/GBARR/IO-1.2301.tar.gz [/geshifilter-code]
Then, you compile and install it:
[geshifilter-code language="bash"] nuno@mac ~ $ tar zxvf IO-1.2301.tar.gz nuno@mac ~ $ cd IO -1.2301 nuno@mac IO-1.2301 $ perl Makefile.PL nuno@mac IO-1.2301 $ make && sudo make install [/geshifilter-code]

I thought it would be enough to fix the problem but an error still persisted.
[geshifilter-code] Use of uninitialized value in concatenation (.) or string at /System/Library/Perl/5.8.8/darwin-thread-multi-2level/Scalar/Util.pm line 30. Catching error: "Undefined subroutine &Compress::Zlib::gzopen called at /System/Library/Perl/5.8.8/CPAN/Tarzip.pm line 122.\cJ" at /System/Library/Perl/5.8.8/CPAN.pm line 359 CPAN::shell() called at /usr/bin/cpan line 198 [/geshifilter-code]
So, according to CPAN's complaint I followed the same steps as detailed above but for Scalar::List::Utils module (source here: http://search.cpan.org/CPAN/authors/id/G/GB/GBARR/Scalar-List-Utils-1.19...).

Finally I ran CPAN and successfully installed the module I wanted. Any road, I recommend to run a CPAN upgrade to ensure all your modules are still consistent.
[geshifilter-code] nuno@mac ~ $ sudo cpan cpan> upgrade [/geshifilter-code]

That's all folks :)