> BTW, do you think that such regexps as ".*" and "^.*$"
> should be supported not only in Dired buffers, but also
> when making replacements in rectangular regions?
> E.g. C-x SPC ... C-M-% .* RET RET should effectively
> clear the region, etc.

After a small refactoring, searching in rectangular regions
is implemented as well: