Fix perth, and the pdf helper tool

Perth is fixed,

But
```
 x = new_x 
```
needs to be
```
 x = new_x unless new_x.nil? 
```
in https://classic.scraperwiki.com/scrapers/ruby_pdf_helper/edit/ - @mlaudner owns it.

We may want to fix that before merging this, and rely on the inclusion.