From perldoc perlfunc, subsection "require":

               Note that the file will not be included twice
               under the same specified name.  The file must
               return TRUE as the last statement to indicate
               successful execution of any initialization code,
               so it's customary to end such a file with "1;"
               unless you're sure it'll return TRUE otherwise.
               But it's better just to put the "1;", in case you
               add more statements.
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-- Randal L. Schwartz, Perl hacker