My docs (different to these docs ->perlman:perlembed) suggest this:

 static void xs_init (pTHX);
 EXTERN_C void boot_DynaLoader (pTHX_ CV* cv);
 EXTERN_C void boot_Socket (pTHX_ CV* cv);
 EXTERN_C void
 xs_init(pTHX)
 {
        char *file = __FILE__;
        /* DynaLoader is a special case */
        newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file);
        newXS("Socket::bootstrap", boot_Socket, file);
 }
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