I seriously doubt that will help in this case. The non-theadsafe part is most likely to be in one of the XS components or their underlying C libraries and will likely manifest themselves regardless of whether the Perlish code is used then cloned into the threads or required into each thread separately.

Working around module non-thread-safety by requireing only really works if you then only make use of the module from a single thread, which wouldn't achieve the OPs goal.