my %keys = (
    a=>1,
    e=>2,
    i=>3,
    o=>4,
    u=>5,
);
my @records = ();
push @records, '1|2|3|d|4';
push @records, '1|2|3|a|4';
push @records, '1|2|3|d|4';
push @records, '1|2|3|o|4';

my @final = ();
my @result = ();
my $re = '';
map {my @flds=split /\|/; push @{$final[$keys{$flds[3]}||0]},$_} @records;

# note that entry 0 is where the unmatched elements wind up...
print map{ "@{ $final[$_] }\n" } grep defined $final[$_],1..$#final;

##</code><code>##

foreach(@records)
{
    my @flds=split /\|/;
    push @{$final[$keys{$flds[3]}||0]},$_;
}