MacOSX 10.8 and 32-bit perl modules
I found a solution to the problem: use the MacOSX 'arch' command to force perl to run as 32-bit.  (See also https://stackoverflow.com/questions/2088569/how-do-i-force-python-to-be-32-bit-on-snow-leopard-and-other-32-bit-64-bit-quest .)

[kw|~] arch -32 perl5.12 -ce 'use Mac::Glue'
-e syntax OK


Note that one needs the explicit "perl5.12" and not simply "perl", since (on MacOSX 10.8) /usr/bin/perl is a shell script which delegates to either /usr/bin/perl5.12 or /usr/bin/perl5.10.