Perhaps I reacted hastily. But the question does sound like a poorly-summarized version of a class assignment.

In an effort to be helpful rather than smug, here are a few suggestions:

• In Perl, it's typical to do textual search/replace with the s/// operator (substitution operator), which is described in perlre, perlop, and perlretut
• If you're dealing with files you'll be opening one for input, one for output, and then at the end maybe replacing the input file with the output file (overwriting). If you need further help with files you may want to ask specifically where you're hung up.
• You will probably be looping, perhaps over lines of an input file. Loops are discussed in perlsyn and perlintro, if I'm not mistaken.

You're most likely to get good help here if you post where you are with respect to the problem. Have you tried something? Do you have a plan of where to begin? Do you have at least a strategy of how you would accomplish the problem as a series of simple steps? Do you have any code written? The more you can give us, and the more specific you can be with respect to your hangups the better we can assist you. But you're not likely to get much help if the sum total of your effort on the project is simply posting a two sentence question here asking someone to do it for you.

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