Unresolved symbols at link time often come from libs and object files getting linked in the wrong order. If one uses a symbol from a library which has already been linked, the later use remains unresolved.

In this case, the error message says butter.obj has a pair of undefined symbols, but it is the last object to be linked. You know that perl56.lib provides those symbols, so linking butter.obj before that lib should work.

Another possibility: #include "ppport.h"

After Compline,
Zaxo