What build of ActivePerl are you using? What error message was reported when you tried the code above? Missing module? (Can't locate HtmlHelp.pm)
With a little searching I found this email in the archives of an Activestate email list
ActivePerl no longer uses that module to generate it's html. It won't
work with any ActivePerl 6xx builds.
Starting with ActivePerl build 617, you can use the following command
line to rebuild the html toc:
perl -MActivePerl::DocTools -e"ActivePerl::DocTools::WriteTOC()"
Note that the html toc is now regenerated automatically after
installing/removing a module with ppm. Any new doc pages included
with a ppm package are now included in the html toc.