This wiki has proven to be less than useful. It's great as user contributed pages (open to anyone with an account), but terrible as a wiki. The new wiki is:
https://trac.parrot.org/parrot/wiki/
Create an account on the site for access to add or edit these scratch pages.
There is a also a wikibook.
PIR Info
PIR is the Parrot Intermediate Representation, used for writing language compilers. Information about PIR can be found at the following links: