I think it's usually better to do this with a reproducible script instead of manual editing in a text editor. There are too many times where the requirements change after the fact for "simple one-off" transformations.
I was going to say the same thing. I think of everything as black boxes, so choice of language is not as important as approach. I would use PHP because it's informal - it's a hybrid between shell and C so expressiveness and speed come basically for free and there isn't much friction. Being able to quickly iterate often makes relationships become apparent at a meta level. For example a quick lookup of a parsing error might reveal that the data was generated by a standard tool, so I could drop what I'm doing and grab that instead. It's not so much about individual choices, but a way of attacking problems that compounded over time leads to a great deal of leverage.