The directory pgplot.patch contains modified/additional files from the 
pgplot 5.2.2 distribution:

  drivers.list               Added ptk to device list
  makemake                   Added ptk compile options
  drivers/pkdriv.c	     Dummy pgplot/tk driver
  drivers/ptk/ptkpgplot.c    Ported code from Tcl/Tk driver
  drivers/ptk/ptkpgplot.h
  sys_linux/...              Modified makedefs for Linux
  sys_sol2/...               Modified makedefs for Solaris
  sys_hp/...                 Modified makedefs for HP-UX

Tk800.022 and Tk800.023 are not compatible. If you wish to compile the
PTK driver with Tk800.022 (and earlier, though I don't guarantee this
will work), you *must* edit the .conf file you will use, and make
uncomment the line:
  OLDPTK=-DOLDTK
If you see a compiler warning such as
  ptkpgplot.c:613: warning: implicit declaration of function `LangWidgetObj'
or make test dies with are error
  undefined symbol: LangWidgetObj
then you are using an incompatible version of Tk. Try either commenting in
or out the OLDPTK definition.

The script patchit.pl (beta quality) will copy *and overwrite* the
patched files into a clean pgplot source directory. Please let me know
if you have problems with this. The script runs from the Tk::Pgplot
directory and takes a single argument, the pgplot source directory.
it tries to check it won't do anything terrible and renames existing
files with a .orig suffix.

The main change to the ".conf" files in the inclusion of the PTK_INCL
definition. I have embedded a small perl script which should figure
out the correct value for this, but is is probably worth verifying the
Makefile if you have compilation troubles. Set the value by hand if
the correct value is not found.

Currently this has been tested under Linux. To get this to work for
other OSes, copy the section from one of the included .conf files the
.conf file for your OS/compile combination.

You must compile the C wrappers to pgplot to get it to work from
Perl. The Tcl/Tk code inserts a dummy driver into the normal libpgplot
so that applications not using the Perl/Tk driver do not have to link
with Perl. When the Perl/Tk driver is wanted the dynamic linker should
load the correct objects.

***NOTE***

Getting the PTK driver to work is a delicate business. Make sure you:
 - Install the Perl/Tk module
 - Install the source code for Tk::Pgplot and patch pgplot
 - Enable PTK driver in pgplot drivers.list
 - Recompile (and re-install) pgplot (make sure libptkpgplot.a is present)
 - Install the Perl PGPLOT module
 - Compile and install Tk::Pgplot (note you should only run perl Makefile.PL
   at this stage).