Blkarray -- extensions and modifications of tabular support

This package is even less supported than any of David Carlisle's other
packages. It was written a long time ago, and is still documented using
the conventions of LaTeX2.09 (although it appears to work with current
LaTeX releases).  It is unlikely that David will be able to work on
this in the foreseeable future, which is why it is published in its
current state.  It is not really a package for using in documents in
its present state, but if you are interested in coding tables of
various sorts in TeX, you may be interested to experiment with it...