Have you ever needed to change the same thing in a load of files and have had to sit there and go through each one in turn and make the same change?
This is a really useful and simple command:
perl -pi -w -e 's/from text/to text/g;' *
It simply goes through all files matching * and runs the regular expression, ‘s/from text/to text/g’ – which means replace all instances of “from text” with “to text”. nifty!