Looking through the documentation for CGI::Session, I see that there are a number of formats for new(); none of which equate to what you have in session2.pl:

my $session = new CGI::Session(undef, $sid, {Directory=>'d:/TBD'});
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Compare that with the equivalent line in session1.pl.

Also, I'd recommend using the Class->new form instead of the new Class form. Take a look at Indirect Object Syntax in perlobj for a discussion of this. It's a good habit to get into and may save you some grief down the track.