FWIW, plx is file extension not name of any ActiveState product
http://docs.activestate.com/activeperl/5.16/Components/Windows/PerlISAPI.html
http://docs.activestate.com/activeperl/5.16/faq/Windows/ActivePerl-Winfaq6.html
http://docs.activestate.com/activeperl/5.16/faq/Windows/ActivePerl-Winfaq2.html
http://docs.activestate.com/activeperl/5.16/PerlEx/Welcome.html
http://docs.activestate.com/activeperl/5.16/PerlEx/PerlExCoding.html
http://docs.activestate.com/activeperl/5.16/faq/Windows/ActivePerl-Winfaq7.html#My_CGI_scripts_don_t_seem_to_run

more tips in the checklists :) Basic debugging checklist , brian's Guide to Solving Any Perl Problem, CGI Help Guide , Troubleshooting Perl CGI scripts, CGI to mod_perl Porting. mod_perl Coding guidelines