I'll answer the latter half of your node later (it's time for lunch), but let me just say that your file-opening-and-reading code is really cumbersome. It's so much easier just to do:

open my($fh), "<", "/path/to/file" or die "can't read /path/to/file: $
+!";
while (my $line = <$fh>) {
  # do stuff with $line
}
close $fh;
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As for line analysis, I'll write something after I've eaten (but I'll be too late, since I'm sure some other monks will give you sound advice).