Thanks for the feedback.
Did you try forcing Math::GMP to link directly to the shared library (rather than linking to the import library) ? I gave that a fair chance of working ... on a hunch, more than anything else :-)
Mind you, whilst I know that gcc can link directly to shared libraries on Win32 and Linux, I have no such knowledge regarding gcc on Macs. And, of course I've got no right to press you like this for details ... so please feel free to ignore.