pwb is one of the packages built into the original metakit based TclKit interpreter.
It contains the proc: librarypath
jcw wrote, 'Pwb is "programmer's workbench", it was added by Matt Newman to collect a number of small utility extensions. I have dropped all those that were not strictly needed for tclkit itself, now that the starkit structure and extension mechanism has evolved further.
The one remaining command in pwb is "librarypath". It will go away once the core deals with setting "tcl_libPath", so one can alter the spot where encoding files live.'