I believe mod_perl.so would need to be rebuilt if the two perl DLLs are sufficiently different in terms of version or binary compatibility (due to different compiler brand or options, etc.). In other words, simply loading the Strawberry DLL in place of the other one might not work. But what happens if you simply try?

That said, do you have any XS (binary) modules installed in your Strawberry module tree, which won't work with the XAMP perl? If not (i.e. if all relevant modules are pure-Perl only), it might be easiest to simply adjust @INC so that the appropriate modules are found and loaded.