Perhaps I should have been more specific/informative.
Take your PostProcess entry, e.g.
PostProcess=/path/to/nzbgetweb/ppweb/nzbget_ppweb.cgi
Enter that path in any command line interface, e.g.
[dave@kt7 ~]$ /path/to/nzbgetweb/ppweb/nzbget_ppweb.cgi
If all is well, you'll get an "It Works!..." message
If the (any) script has DOS line endings, or a wrong interpreter path, the shell will return
...bad interpreter: No such file or directory
A bad path will return
...No such file or directory
If the (any) script is "calling something funny within it", or contains a typo, the interpreter (Perl in this case) will return a detailed message, e.g.
Can't locate... line 5
Bareword found where operator expected... line 17
To see if PPWeb works as a CGI script, add the PPWeb portion of the path to your NZBGetWeb URL, e.g.
http://nzbgetweb.domain.tld/ppweb/nzbget_ppweb.cgi
http://192.168.1.1/ppweb/nzbget_ppweb.cgi
If all is well, you'll get an "It Works!..." page
If there are any problems, you'll get a stock (for now) '...Premature end of script headers... Error 500' page. Look in your server log for the interpreter messages. When using Apache mod_suexec, be sure to check the suexec_log for any ownership/permission issues.
When you have the script configured/setup properly (you got the "It Works!..." messages) and something doesn't work, use the PPWeb Log links (tailed html versions of your nzbget and server logs) to view the error messages (or check the logs directly).