my($n1,$n2,$letter,$ordinal,$name,$code) = 
              (my @record = split(/[\s,]+/,$_));
  push (@DB, [@record]);
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You are needlessly copying the array to a new array:

  my ( $n1, $n2, $letter, $ordinal, $name, $code ) = 
              my @record = split /[\s,]+/;
  push @DB, \@record;
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(@{$hash{"$name$code"}})[-1]
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That is usually written as $hash{"$name$code"}[-1].   You are needlessly copying the array to a list.

   my ($a_ordinal,$a_name) = (@$a)[3,4];
   my ($b_ordinal,$b_name) = (@$b)[3,4];
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Again, you are needlessly copying the array to a list.   That is better written as:

   my ( $a_ordinal, $a_name ) = @{ $a }[ 3, 4 ];
   my ( $b_ordinal, $b_name ) = @{ $b }[ 3, 4 ];
[download]