Well, something along the lines of:

perl -ne 'print if /^("This is really important"|"This is very importa
+nt to you"|"This is also important")$/' dread.log > warnings.txt
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Or, more verbosely:

use strict; use warnings;
open DREAD, "dread.log" or die "Can't open input file";
open OUT, ">warnings.txt" or die "Can't open output file";
while (<DREAD>) {
  print OUT if /^("This is really important"|"This is very important t
+o you"|"This is also important")$/;
}

close DREAD;
close OUT;
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The hardest part is getting the regexes right, to match only lines you're interested in. To be more accurate, you have to provide a realer (?) example.