As elusion just pointed out to me, you do have the -w in your code, I'll shut up (though if you had run this from the command line you would have seen the error, and there is no reason why you can't run a CGI script from the command line for testing).

You could also take a look at using use CGI::Carp qw(fatalsToBrowser); which might help next time.

In addition to what elusion has already said, if you had had use warnings; at the top of your code or -w on your shebang (#!) line, you would have got the error message:

Reversed -= operator at C:\test\192744.pl line 24. telling you exactly the problem.