The programs 'addspi' and 'spifilter' are written in Perl and require
the PDL and Astro::FITS::CFITSIO modules. They have been tested on a
variety of systems - Linux, OS X and Solaris on x86 and Sparc
hardware, both 64 and 32 bit. In general, it is recommended that
newer versions of PDL and Astro::FITS::CFITSIO be used, although the
programs have been tested successfully with older versions, back to
PDL v2.4.1 and Astro::FITS::CFITSIO v1.01.

addspi: append SAMP and SPI columns to an HRC-S event list. Normally
  called as
    $ addspi input_evt.fits output_evt.fits
  or try
    $ addspi -h
  for available options.

spimeanfits.fits: gain map used by addspi

spifilter: filter an HRC-S/LETG event list on SPI. Usually called as
    $ spifilter input_evt.fits output_evt.fits
  or give argument -h for a list of available options.

spifilter.spec: SPI filtering specification as a function of
  wavelength, used by spifilter
