Forest v2.1.1

Changes:

1. Minor improvements
   • Implemented argument processor instruction \index{processor>p}.
2. Bugfixes
   • Argument processor instruction u introduced an extra layer of braces
     around each result item.
   • Argument processor instructions l and L did not always load the
     desided number of arguments.
   • Argument processor instructions and and or were taking the
     arguments from the start of the left side instead of its end.