The numbering plan in our company has changed and all phone numbers that start with a 1 get a 2 inserted after the second digit. This means e.g 1423 should become 14223. A collegue has manually edited the list and accidently inserted some spaces at the beginning of some lines. Now you would like to replace variable temp by the variable named counter. If the string temp is just replaced with counter then temporary becomes counterorary which is not really what you want.
Regular expressions can do it.
That is, temp and not the letter o. I hope that this article did catch your interest. Now you might want to have a look at the man-pages and documentation of your favorite editor and learn the details. Have fun, happy editing.