At first, I was a bit confused by this:

while (<@ARGV>)
{
  ...
}
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If the intention is to read the contents of one or more files named on the command line, this is usually expressed as just:

while (<>)
{
  ...
}
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When you do it this way, you are free to choose whether to name input files as command line args, or to pipe data to the script from some other process instead -- that is, the following two usages would be equivalent:

your_script  file1 file2 file3

cat file1 file2 file3 | your_script
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That's a dumb example, but the point is that if you happen to use some other process to generate those files, you could do:

other_process | your_script
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It's just a nice kind of flexibility to have.