Use a hash to store the information whether or not a record has been seen already. Use the record as key. 

use strict;
use warnings;
$/="\n\n";
my %seen;
while(<DATA>){
  print unless $seen{$_}++;
}
__DATA__
a

b

b

a

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In reply to Re: How to remove duplicate records by hdb
in thread How to remove duplicate records by SatisfyMyStruggles

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