Here's a fun parsing example though...

use MooX::Struct
    Record => [qw( $id $et @ac $os $pt @rs @ra )],
    Person => [qw( $surname $initials )],
;
use Data::Dumper;

my %IS_PERSON = (
    ra => 1,
);
my %IS_LIST = (
    ac => 1,
    rs => 1,
    ra => 1,
);

my %record;
my @records;
while (<DATA>) {
    chomp;
    my ($field, $value) = /^(..)\s*(.+)$/;
    $field = lc $field;
    
    if ($field eq 'id' and keys %record) {
        push @records, Record->new(%record);
        %record = (); # start new record
    }
    
    if ($IS_LIST{$field}) {
        push @{$record{$field}},
            map { $IS_PERSON{$field} ? Person[split] : $_ }
            split m{,\s*}, $value;
    }
    else {
        $record{$field} = $IS_PERSON{$field} ? Person[split / /, $valu
+e] : $value;
    }
}

# EOF, push last record
push @records, Record->new(%record);


print $records[1]->ra->[0]->surname;


__DATA__
ID   AaaI
ET   R2
AC   RB00001;
OS   Acetobacter aceti ss aceti
PT   XmaIII
RS   CGGCCG, 1;
RA   Tagami H., Tayama K., Tohyama T., Fukaya M., Okumura H., Kawamura
+ Y., 
RA   Horinouchi S., Beppu T.;
ID   AaaII
ET   R2
AC   RB00001;
OS   Acetobacter aceti ss aceti
PT   XmaIII
RS   CGGCCG, 1;
RA   Horinouchi S., Beppu T.;
ID   AaaIII
ET   R2
AC   RB00001;
OS   Acetobacter aceti ss aceti
PT   XmaIII
RA   Horinouchi S., Beppu T.;
RS   CGGCCG, 1;
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