We've used 'nm' to check if the missing symbol is defined in our-app: Yes it is!

Well it shouldn't be, all the symbols are supposed to be defined in perl516.dll

It looks like you're mixing a threaded+unthreaded or 32bit/64bit perl somehow, or just another LD_LIBRARY_PATH issue

Like MD5.so was compiled for a different version of perl... Perl_Istack_sp_ptr error