It tells the command shell to send all output from filehandle 2 (typically STDERR) to filehandle 1 (typically STDOUT). For further details, see perldoc perlop:

   qx/STRING/
   `STRING`
      A string which is (possibly) interpolated and then executed as
      a system command with "/bin/sh" or its equivalent.  Shell wild-
      cards, pipes, and redirections will be honored.  The collected
      standard output of the command is returned; standard error is
      unaffected.  In scalar...

      <<<<< SNIP >>>>>

      ...To capture a command's STDERR and STDOUT together:

         $output = `cmd 2>&1`;
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