In GNU Emacs 23.0.50.4 (i686-pc-linux-gnu, GTK+ Version 2.10.13)
 of 2007-09-14 on escpc40
Windowing system distributor `The X.Org Foundation', version 11.0.10300000
configured using `configure  '--with-gtk''

add-change-log-entry-other-window stopped detecting the current
subroutine in perl/cperl-mode due to, I think, this change:

    revision 1.189
    date: 2007-07-20 21:30:51 +0100;  author: monnier;  state: Exp;  lines: +15 -15;  commitid: 9SIF7GuRLekDZxqs;
    (add-change-log-entry, add-log-current-defun, change-log-merge):
    Use derived-mode-p rather than checking major-mode directly.

The attached patch seems to fix it.

Thanks,
Matt