You can make this shorter with the command-line switches in perlrun. In fact if you toss in a little knowledge about how line ending issues work, the following when run on a Windows machine will turn Unix, DOS, or Mac line endings into DOS endings:

perl -pi.bak -e 1 file1 file2 file3
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On Unix you can convert to local text format with:

perl -pi.bak -e 's/\r\n?|\n\r?/\n/g' file1 file2 file3
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That should work on MacOS as well, but I don't have it here to test. (I would be able to get it to work on all 3 platforms, but DOS likes to use " to group arguments in the command line, while Unix likes to use ' for the same purpose. I couldn't figure out how to get around that incompatibility in one line.)