Are the records that are duplicate exactly the same? Do you care about the order of the records when you print them out again? You can use a hash to speed things up:

my %uniq=();
open(LIST, 'file.txt') or die "Error 1";
while(<LIST>) {
chomp;
$uniq{$_}=1;
}
close(LIST); 
#the %uniq hash keys now contain all the records with duplicates remov
+ed
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HTH