Perl5 リファレンス

       bless REF,CLASSNAME

       bless REF
               This function tells the thingy referenced by REF
               that it is now an object in the CLASSNAME package.
               If CLASSNAME is omitted, the current package is
               used.  Because a `bless' is often the last thing
               in a constructor, it returns the reference for
               convenience.  Always use the two-argument version
               if the function doing the blessing might be
               inherited by a derived class.  See the perltoot
               manpage and the perlobj manpage for more about the
               blessing (and blessings) of objects.

               Consider always blessing objects in CLASSNAMEs
               that are mixed case.  Namespaces with all
               lowercase names are considered reserved for Perl
               pragmata.  Builtin types have all uppercase names,
               so to prevent confusion, you may wish to avoid
               such package names as well.  Make sure that
               CLASSNAME is a true value.

               See the Perl Modules entry in the perlmod manpage.