Perl5 リファレンス

       return  Returns from a subroutine, `eval', or `do FILE'
               with the value given in EXPR.  Evaluation of EXPR
               may be in list, scalar, or void context, depending
               on how the return value will be used, and the
               context may vary from one execution to the next
               (see `wantarray').  If no EXPR is given, returns
               an empty list in list context, the undefined value
               in scalar context, and (of course) nothing at all
               in a void context.

               (Note that in the absence of a explicit `return',
               a subroutine, eval, or do FILE will automatically
               return the value of the last expression