Reminiscent of the 2>&1 syntax of many shells, this line instructs perl to send standard error to the same place it sends standard out.

We made the corrections to the code, but now we are getting this error:<BR><BR>Can't modify addition (+) in scalar assignment at H"\administrator\ActivePerl\Perl\calculator.plx line 16, near ...

Well, I didn't see much in the module documentation for Net::SSH: erl, so you may want to encapsulate the problem code in an alarm with some sort of reasonable timeout.