We have the bug report ID: 2817882 "frame not documented".
I think the function $frame does not give any useful information, when
called from the user. We should make the function invisible and
introduce a CL symbol. I would like to suggest to replace "$frame" with
"break-frame". This name would match the existing naming scheme for the
functions of the Maxima debugger.
Remark: It is easy to replace $frame. We have only 4 calls in
mdebug.lisp and one call in imaxima.lisp.
Dieter Kaiser