VERSION( [NEED] )
           "VERSION" returns the version number of the class (package).  If
           the NEED argument is given then it will check that the current ver‐
           sion (as defined by the $VERSION variable in the given package) not
           less than NEED; it will die if this is not the case.  This method
           is normally called as a class method.  This method is called auto‐
           matically by the "VERSION" form of "use".

               use A 1.2 qw(some imported subs);
               # implies:
               A->VERSION(1.2);