[texhax] Advanced Ligature Handling in .pl Files

[Barbara Beeton]

don knuth wrote an article on virtual fonts
that was published in tugboat 11:1.  a
scanned pdf of that article can be found at

   http://tug.org/TUGboat/Articles/tb11-1/tb27knut.pdf

basically it contains an excerpt from vftovp.web
with a brief introduction.  it mentions the
ligature mechanism, but doesn't go into details
of how to use it.  however, it refers to another
article, by yannis haralambous,

   http://tug.org/TUGboat/Articles/tb10-3/tb25hara-latin.pdf

that contains an example of using the mechanism
to support the accented letters in most modern
european languages.  maybe that might help.
 							-- bb

---------- Original message ----------
Date: Sun, 13 Sep 2009 11:20:19 -0500
From: Stan <texforeverything at att.net>
To: texhax at tug.org
Subject: [texhax] Advanced Ligature Handling in .pl Files

I would like to use some of TeX's (Metafont's?) smarter ligature capabilities 
(described under the headings "smarter ligatures" and "boundary ligatures" in 
the article www.tug.org/TUGboat/Articles/tb10-3/tb25knut.pdf) in fonts for 
which I already have .tfm files.  I've successfully specified some ligatures 
("ff", "fi", etc.) using what I learned from this page:

http://www.slac.stanford.edu/comp/unix/package/tex/web2c/web2c_10.html

but this page does not talk about the more advanced ligature handling.  (I used 
tftopl on the .tfm file for the font in question, added some entries to the 
ligtable, and then converted the .pl file back to a .tfm using pltotf.  This 
process worked for "standard" ligatures.)  I tried variations on the syntax 
specified in the Tugboat article, as well as on pages 316 and 317 in appendix F 
of The Metafont Book, but that doesn't seem to be for .pl files.

Is there a way to specify the more advanced ligature handling in .pl files? 
Also, are there any other resources that discuss the syntax to use in .pl 
files?

Thanks for any help.