Often, I have a big log file and I know in which section I want to search. Typical example is that I want to see what happens to "widget" between two events or timestamps. I'd like to first search to find the events, timestamps or whatever limits my section, mark these lines as section-begin and section-end, and then have all search commands be limited to this section. If only one of section-begin and section-end is set, the other is assumed to be start / end of file.