/usr/share/doc/m4/examples/comments.m4 is in m4 1.4.18-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | # An ordinary comment
define(`foo', # A comment in a macro
`Macro `foo' expansion')
foo
define(`comment', `*** Macro `comment' expansion ***')
changecom(`@', `@')
foo
|