Emacs completely frozen - is it interesting? 19.33 .. 21.2

[Ilya Zakharevich <nospam-abuse@ilyaz.org>]

Debugging a problem in CPerl mode, I found (yet another?) way to
completely freeze emacs (short of core dump, nothing interrupts it).
I can reproduce it on all versions I have, from (patched) 19.33 to
21.2.1.

If this is interesting, here is the scenario:

  emacs -l ./cperl-mode.elc -q attrs.pl

(give -nw if you like).  Now do

  M-x font-lock-mode

then go to the 

  =cut

line in the file, and delete the last character.  Apparently, no
obvious function defined in cperl-mode.el is entered at this time.

CPerl mode should be v5.11; it (and attrs.pl) is available on

  ilyaz.org/software/emacs

(the file for cperl-mode is marked as "broken" to indicate the problem).

Can people reproduce it with newer versions?

Hope this helps,
Ilya