After many more hours of searching I came to the same conclusion. The callback example that I referenced was implemented as a DLL and invoked using the Win32::API.

Unfortunately, using PerlNET is not an option for me; although I do agree it would make things a lot simpler.

Currently I am trying to implement a work around by defining pure-Perl intermediary functions using PerlEzEvalString, then having those functions modify magic scalars to pass data back to C. At first glance this approach appeared promising; however, providing the correct return type format for the PerlEzSetMagicScalarFunctions function pointers is proving to be rather difficult (but that is more a C problem than a Perl issue).

I was only able to find one code example relating to magic scalars with PerlEZ (PerlEzSetMagicScalarFunctions), and the documentation at ActiveState appears to be a little thin. Do you know of any other examples?