I configured Hudson job to poll Perforce for changes to only build changed modules, however, after polling Hudson, continues with a complete build even when nothing has changed. This causes all sub-modules to cascade build when nothing has changed.

When looking at the details of the job, Hudson reports:
No changes from last build.
Started by an SCM change

Then looking at the console, I can see the complete build has executed.

Screenshot of Perforce configuration:
http://screencast.com/t/ZGI3NGI1MG

Screenshot of Hudson job details:
http://screencast.com/t/OGQyZGFiND

Screenshot of Hudson job changes (from last build):
http://screencast.com/t/NDU5OWQ5YmM

Screenshot of Hudson console showing complete build:
http://screencast.com/t/ODUxYTgx