Check out the howto.

update: I'm not a apache 2.2 expert by anymeans but I think you're going to want something like this in your httpd.conf:

<Directory /usr/local/apache/htdocs/*/cgi-bin>
  Options +ExecCGI
</Directory>
[download]

That being said ... I think one of the drawbacks to your approach is your exposing way too much of your underlying architecture. User's are going to see something like this:

http://bioinfo-z.comp.nus.edu.sg/Test/cgi-bin/foo
http://bioinfo-z.comp.nus.edu.sg/WebApp1/cgi-bin/bar
http://bioinfo-z.comp.nus.edu.sg/WebApp2/cgi-bin/baz
[download]

I think a better approach would be to either use virtual servers:

http://test.comp.nus.edu.sg/cgi-bin/foo
http://webapp1.comp.nus.edu.sg/cgi-bin/bar
http://webapp2.comp.nus.edu.sg/cgi-bin/baz
[download]

Or something like CGI::Application

http://bioinfo-z.comp.nus.edu.sg/cgi-bin/test?mode=foo
http://bioinfo-z.comp.nus.edu.sg/cgi-bin/webapp1?mode=bar
http://bioinfo-z.comp.nus.edu.sg/cgi-bin/webapp2?mode=baz
[download]