perl-mode backward-sexp strangeness

[Mosur Mohan]

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In GNU Emacs 21.1.1 (i686-pc-linux-gnu, X toolkit)
 of 2001-11-13 on filc6001
configured using `configure  --prefix=/usr/intel/pkgs/emacs/21.1 
--x-includes=/usr/X11R6/include:/usr/intel/pkgs/xpm/3.4k/include:/usr/intel/pkgs/jpeg/6b/include:/usr/intel/pkgs/libpng/1.0.6/include:/usr/intel/pkgs/tiff/3.5.5/include:/usr/intel/pkgs/zlib/1.1.3/include:/usr/intel/pkgs/libungif/4.1.0b1/include:/usr/intel/pkgs/ncurses/5.1/include
 
--x-libraries=/usr/X11R6/lib:/usr/intel/pkgs/xpm/3.4k/lib:/usr/intel/pkgs/jpeg/6b/lib:/usr/intel/pkgs/libpng/1.0.6/lib:/usr/intel/pkgs/tiff/3.5.5/lib:/usr/intel/pkgs/zlib/1.1.3/lib:/usr/intel/pkgs/libungif/4.1.0b1/lib:/usr/intel/pkgs/ncurses/5.1/lib
 --without-toolkit-scroll-bars'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: C
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

In a perl-mode buffer, I have a line that says:
  $instloc = 0;

Put the cursor on the 'n' of $instloc (i.e., the 2nd char of the variable),
and do \C-M-b, i.e., (backward-sexp): it moves to the 'i', not the '$'
Put the cursor on any other character of $instloc and do \C-M-b and it
moves to the '$'.

Why this difference?


Recent input:
C-n C-n f o r e a c h SPC $ f i l e SPC M-( @ f l i 
s t C-e SPC M-{ C-n C-e { C-j $ i n s t l o c SPC = 
SPC 0 ; M-m C-f C-f C-M-b C-f C-f C-f C-M-b M-x M-p 
<return>

Recent messages:
Auto-saving...done
Auto-saving...done
Loading newcomment...done
Auto-saving...done
Undo! [6 times]
C-M-b runs the command backward-sexp
C-c C-c runs the command mail-send-and-exit
report-emacs-bug-hook: M-x report-emacs-bug was cancelled, please read *Bug 
Help* buffer
Mark set
Sending...done