Tree style (files) explorer for p9p acme.
If you're not an acme user, here's the easiest way to get acquainted: http://research.swtch.com/acme
Otherwise, you know the drill: button 3 (usually right click) to unfold/fold directories (the ones marked with a '+'. Same click on a regular file sends it to the plumber, so default behaviour will be to open it if it's text. Button 2 (middle click) on an element of the tree prints the full path of the element in the +Errors window.
B2 on Win or Xplor commands opens a new win (or a new xplor respectively), by default at the same root directory as their parent. However, they make use of chording 2+1: just position your cursor wherever you want in the tree, then button 2 on Win or Xplor, hold it, and at the same time press button 1. Tadaaa! behold the chording magic!
DotDot redraws xplor with the root set as the parent directory.
Hidden toggles displaying the hidden files/directories. It does not redraw the tree.