plain TeX: undefined control sequence \protected

[Rodolfo Medina]

Hi all.

After upgrading TeXlive in my Debian system, the simple folowing example:

\input color

hallo

\vfill\eject\end

processed with simply `tex test, produces the following error:

$ tex test
This is TeX, Version 3.141592653 (TeX Live 2022/Debian) (preloaded format=tex)
(./test.tex (/usr/share/texlive/texmf-dist/tex/plain/graphics-pln/color.tex
(/usr/share/texlive/texmf-dist/tex/plain/graphics-pln/miniltx.tex
! Undefined control sequence.
l.548   \protected
                  \def\mathcolor{\begingroup\@ifnextchar[\mlx at mathcolora\mlx...

? 


Please help with this issue.

Thanks,

Rodolfo