ObRandomTip: To avoid making the mistake:

if ($x = 1) {
  # etc
}
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get into the habit of trying to put the variables on the right, not the left. It looks strange, but:

if (1 = $x) {
  # etc
}
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is likely to give you a much more informative error message. (This habit will serve you in good stead in quite a few languages, not just Perl.)