rrdtool and perl 5.10 not playing nice

[Rob Byrnes]

I have seen this issue on two machines now, but this particular
instance is on a newly built one.

I run munin to collect and graph stats on my network from this box.
net-mgmt/munin-master depends on perl and rrdtool. I installed perl
5.10 from ports and then installed munin-master. rrdtool was built as
a dependency with the default port knobs:

root at aylee /usr/ports/databases/rrdtool # make showconfig
===> The following configuration options are available for rrdtool-1.4.3:
     DEJAVU=off "Use DejaVu fonts (requires X11)"
     MMAP=on "Use mmap in rrd_update"
     PERL_MODULE=on "Build PERL module"
     PYTHON_MODULE=off "Build PYTHON bindings"
     RUBY_MODULE=off "Build RUBY bindings"


I'm seeing this error from munin:

Can't locate RRDs.pm in @INC (@INC contains:
/usr/local/lib/perl5/5.10.1/BSDPAN
/usr/local/lib/perl5/site_perl/5.10.1/mach
+/usr/local/lib/perl5/site_perl/5.10.1
/usr/local/lib/perl5/5.10.1/mach /usr/local/lib/perl5/5.10.1 .) at
+/usr/local/lib/perl5/site_perl/5.10.1/Munin/Master/Utils.pm line 22.
BEGIN failed--compilation aborted at
/usr/local/lib/perl5/site_perl/5.10.1/Munin/Master/Utils.pm line 22.
Compilation failed in require at
/usr/local/lib/perl5/site_perl/5.10.1/Munin/Master/UpdateWorker.pm
line 18.
BEGIN failed--compilation aborted at
/usr/local/lib/perl5/site_perl/5.10.1/Munin/Master/UpdateWorker.pm
line 18.
Compilation failed in require at
/usr/local/lib/perl5/site_perl/5.10.1/Munin/Master/Update.pm line 17.
BEGIN failed--compilation aborted at
/usr/local/lib/perl5/site_perl/5.10.1/Munin/Master/Update.pm line 17.
Compilation failed in require at /usr/local/share/munin/munin-update
line 13.
BEGIN failed--compilation aborted at
/usr/local/share/munin/munin-update line 13.

RRDs.pm does exist:

root at aylee /root # find /usr/local/lib/perl5 -name RRDs.pm
/usr/local/lib/perl5/site_perl/5.10.1/Log/Log4perl/Appender/RRDs.pm

Not knowing anything of perl, what can I do to fix this?  It has only
occurred since upgrading to/installing perl 5.10

cheers,
Rob