Wildcard matching in debbugs-gnu-search - how?

[Michael Heerdegen]

Hi,

I've read the debbugs-ug manual now (ok, partly, and not far enough to
find out what "-ug" stands for).

My question: With the newest version of debbugs-gnu, why doesn't, for
example,

(debbugs-gnu-search "[RX] ^el-search-.*-sources$" nil nil nil nil)

give me matches but

(debbugs-gnu-search "el-search-emacs-elisp-sources" nil nil nil nil)

finds one - what's wrong with my given RX syntax?  I also fail trying to
use [BW] and [EW].  BTW, are these operators also allowed when
specifying the subject, or only for the body?

TIA,

Michael.