>> There are a bunch of LaTeX packages that only work with a specific
>> TeX engine, and which need special input code for that. For
>> example, `fontspec` (with its excellent OpenType support) only
>> works with XeTeX and luatex. Or think of 'lyluatex', which
>> obviously needs luatex.
>
> Yes, absolutely. This is exactly why I am surprised that some people
> set global environment variables that select a TeX engine "to always
> use the same". What tools do they have an effect on?
Looking at the TeXLive scripts, I see at least `texi2pdf` and
`pdfxup`. However, I guess there are more programs that listen to
`PDFTEX` and/or `PDFLATEX`, for example 'scons'.
Werner
