I think the (ahem!) key here is to convert your @keys array into a hash to make it easier to check for the existance of keys in your data line.

my @keys = ( qw|a e i o u| );
my %keys = map { $_ => 1 } @keys;
my @records = (
  '1|2|3|d|4',
  '1|2|3|a|4',
  '1|2|3|d|4',
  '1|2|3|o|4',
);

my @final;
my @result;

foreach (@records) {
  if ($keys{ (split /\|/)[3] }) {
    push @result, $_;
  }
}

print map { "$_\n" } @result;
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