It should be noted that there are some caveats when compiling extensions with a different version of the compiler than that which compiled the Perl (which is the case when building modules for ActivePerl with the Visual C++ Toolkit), this is due to the fact that the C runtime libraries will reside in different DLLs so OS level objects that might be shared between Perl and the extension that are defined in the runtime (such as HANDLEs and so forth) will not be valid in the part that didn't define them. I was recently caught out by this with respect to Term::ReadKey and it is discussed here

Of course modules that don't share C runtime thingies with Perl shouldn't be affected by this.

/J\