You would open a single file for append/output. You would then, open one input file, read it line by line, and as you read each line, write it back out to the output file. When you reach the end of the first file, you would then close it and open the second input file, and so on. Once you've repeated this process for each input file, you would then close the output file. Don't forget to check return values to ensure that your files are getting opened and closed properly, etc.

You may be able to glean some understanding by reading the documentation for open. Also perlopentut may be helpful.

Take a stab at it, and when you get hung up on some specific part of your implementation of a solution, follow-up to this thread with some specific questions.

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