Math::BigInt returns references to blessed scalars, and uses overload to cause it to be stringified when you refer to it in a string. You put the reference directly into the argument block used by CGI::Cookie, and CGI::Cookie doesn't know what to do with it. Simple solution: force it to be stringified:

$c = new CGI::Cookie(-name    =>  'NetAppliance1.0',
                     -value   =>  "$id",
                     -path    =>  '/cgi-bin/'
                     -secure  =>  0
                    );
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Data::Dumper is often your friend in these circumstances:

use Data::Dumper;

print Dumper({-value => $id});
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produces:

$VAR1 = {
          '-value' => bless(do {\(my $o= '+123456789123456789')}, 'Mat
+h::BigInt')
        };
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Which is a good indication that things are not as you thought :-)

Andrew. (You should really be using CGI.pm throughout)