Thanks. It was a little bit confusing figuring out what order all the modules mentioned in the error messages should be installed in. This is the order that worked for me:

1) HTML::Parser
2) HTML::TreeBuilder
3) HTML::Element (a message said it was up to date)
4) HTML::Tree (a message said it was up to date)
[download]

Then I tested HTML::Tree in a program, and it worked.

Thanks for all the help!