Sorry. Here it is.
$ luatex old
(./old.tex
! Undefined control sequence.
l.2 \newcounter
{FancySomeLine}
?
old.tex
-------
\newcount\FancyAnyLine
\newcounter {FancySomeLine}
Hello.
\bye
May be rubbery stuff I wouldn't know about. Apologies it that's it.