> But I don't know what are you going to do with the combining accent
> appearing after the letter.
Three possibilities occur to me.
1) make every character active and look ahead to see if it is being
followed by a combining char.
This is possible and fun to code in TeX but I don't really think it
is a long term stable solution.
2) use perl (or anything else) to detect all combining characters
and replace them by some command placed before the base.
This is quick and easy to arrange, but if you are having a perl
pre-pass before TeX, it may as well go further and decode the
entire character stream into "latex internal form" ie 7bit ascii tex
markup. In which case we may as well stay with that markup as latexs
3) use an underlying "tex" engine that understands unicode combining
characters (and the unicode bidirectional algorithm) and other
features of the unicode character properties. (and probably also xml
document syntax as well)