When trying to do grid typesetting in plain TeX I stumbled upon old upages, which looks very promising (see also this introduction). So I opened upages-20001214.tar.gz and put everything in uplain/upages/ in a directory.
To test the package, I created a minimal file saying
\input upages
bla bla bla
\bye
and tried to compile this. However, XeTeX chokes on a certain line:
This is XeTeX, Version 3.14159265-2.6-0.99991 (TeX Live 2014/Arch Linux) (preloaded format=xetex)
restricted \write18 enabled.
entering extended mode
(./gridtest.tex (./upages.tex (./umaster.tex
! Undefined control sequence.
l.519 \def\@innernewread
{\alloc@6\read\chardef\fift@@n}
?
! Emergency stop.
l.519 \def\@innernewread
{\alloc@6\read\chardef\fift@@n}
No pages of output.
Transcript written on gridtest.log.
Why does it say ‘Undefined control sequence’ if that macro is just to be \defined? The strange thing is: I remember using upages years ago and it compiled just fine. Even now, when trying just tex gridtest, it compiles fine, but using pdfTeX or XeTeX, it spits out this error.