eliminate subwords in dpkg --search?

[Marcel Fehr <fehr@labex.ch>]

hi there

How do I search for a explicied pattern within all my installed packages?

for e.g if I want to look which package owns the command cu, a "dpkg -S cu"
will list all package where's a pattern starting with cu (cups, custom, ... 
same
as I would do "dpkg -S cu*"). Is there a way to limit that?

And is it possible to shapen the scope so that it looks
into all available packages on the installation medium rather
into the installed ones only?  Would avoid to check
http://www.debian.org/distrib/packages#search_contents all the times :).

thx in advanced, Marcel