me@host> perl -c XXA.pm 
Beginning XXA compile
  Beginning XXB compile
    Beginning XXA compile
      Just used XXB in XXA compile
     Finishing XXA compile
    XXA->import called
    Just used XXA in XXB compile
   Finishing XXB compile
  XXB->import called
  Just used XXB in XXA compile
 Finishing XXA compile
XXA.pm syntax OK
me@host>