perl-mode: indent in empty buffer

[Kevin Ryde]

In GNU Emacs 21.1.1 (i386-debian-linux-gnu, X toolkit)
 of 2001-10-22 on raven, modified by Debian
configured using `configure  i386-debian-linux-gnu --prefix=/usr 
--sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib 
--infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes --with-x=yes 
--with-x-toolkit=yes'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  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: C
  locale-coding-system: nil
  default-enable-multibyte-characters: t


Under "emacs -q -no-site-file" with an empty buffer in perl-mode,
pressing Tab gives the following error,

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
  perl-indent-line("\f\\|;?#" 1)
  perl-indent-command(nil)
  call-interactively(perl-indent-command)

A similar error occurs on pressing M-;

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
  perl-indent-line()
  indent-according-to-mode()
  comment-dwim(nil)
  call-interactively(comment-dwim)

If the buffer is non-empty, a single newline for instance, this
doesn't happen.  Obviously it's not particularly important, but
probably shouldn't throw an error.