For command line, I prefer awk and sed. Yes, I know they don't have the power of Perl or Python for big projects, but this is an excellent example of using a shotgun to kill flies.
Edit: And of course, since this same site has awesome examples of sed and awk one-liners in action, the comparison has never been easier to make.
For these sorts of examples, I tend to use awk and sed too, but sometimes the shotgun is useful. One major advantage of using Perl in this context is that you also have -M, with all of CPAN at your disposal.
Edit: And of course, since this same site has awesome examples of sed and awk one-liners in action, the comparison has never been easier to make.