Question about tor and circuits.

[J.L.Cooper at lboro.ac.uk]

Hi,
  Am I correct in thinking that if tor only has one circuit active it will try to create more, or is this time based?

  If that is the case is it possible to get tor to stop creating circuits except where I have requested specific ones through the control interface.

  What I am attempting to do is use a Perl script I have created that uses the control interface to close down existing circuits, create a new one (with just one hop as I am not after anonymity) and then use it to retrieve a web page. This process is then repeated using different exit nodes.  Quite a simple project to start with, but I keep finding that when I list the circuits tor has created other ones so I don't know for certain which circuit is being used.

Regards,
  Jason Cooper