People talk about one-liners, but it's usually just to say that someone's usefull little utility could be collapsed into an unreadable glumph of line noise .... wait, that's the deinition of Perl, isn't it?
But what one-liners do people actually use? I regularly alter Autosys meta-scripts to run a new version of a set of scripts, or to target a new database, or to run on a new host, using perl as a super-sed:
co -l *np40*
perl -pi -e"m/host:/ && s/paias167/pa167c1n1/"
ci -u -m'move scripts to new hosts' *np40*