As per .LRN 1.0.1 installation instructions, ran:

./configure --with-aolserver-src=/tmp/src/aolserver/aolserver --with-tcl=/usr/lib/tcl8.3

But when running make, the build system couldn't find the tcl header files.
I found the easiest solution was to symlink all the files I could find in /usr/include/tcl8.3 into this source package's include directory. [NOTE: I later found that these header files are in the aolserver/aolserver/include directory]

Unfortunately, another step in the installation requires the building of supplemental modules which must be constructed from a PostgreSQL source tree that includes the contrib directory. These sources, I don't have available since I have a Debian package installed. But even if I had the corresponding sources, I don't even know if PostgreSQL 7.2.1 would even work for these installation instructions, which presuppose 7.2.4.

At this point, I'm going to postpone an attempt at installing this feature. When .LRN 2.0 comes out, it's possible that it will support PostgreSQL 7.3 in which case we can install the Debian package (of testing status) which might already include this contributed module pre-compiled.