Yes, but where do you stop? At the end of that road is:

    $i++;  # Add 1 to $i
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IMO, if you have to document the syntax, you should rewrite the code. Now, I don't think:

  ($copy = $orig) =~ s/PATTERN/REPLACEMENT/;
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is obscure. It shouldn't need comments. If you feel you're among novices or bad programmers, still don't comment the code. Rewrite it in baby steps.