I've found the OSX system Perl more restrictive than most in that even as root you are unable to write to /usr/bin and similar trees which makes the binding of external libraries significantly more problematic.
I'd always ended up installing another version on OSX and things would stabilise but I always felt a little dirty running multiple versions. Thanks for the advice - I now at least feel somewhat better informed and now also know not to write the system Perl as Mac Perl.
Another take-away for me was also that brew install perl != perlbrew. I think that spending a little more time exploring these on a new setup has given me a little more confidence as to what is going on. Next on the list is writing some local modules with C library bindings which is something I've always wanted to do but never got around to - while playing around this level and with a little time on my hands I think I'll have a crack.
Thanks for the advice.