in reply to
What one-liners do people actually use?
I agree with some of the posts above, any one-liner of even moderate complexity that I use regularly will be turned into a script and/or alias. I'm lazy that way :-). Partly because of that, my most often used perl-related one-liner has to be
prove -vl t/
Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. -- Brian W. Kernighan