Adding a default FMT field when none is given

Build.PL

@@ -1,5 +1,5 @@
 
-# This file was automatically generated by Dist::Zilla::Plugin::ModuleBuild v6.005.
+# This file was automatically generated by Dist::Zilla::Plugin::ModuleBuild v6.008.
 use strict;
 use warnings;
 

README.md

@@ -44,6 +44,7 @@ Catmandu::MARC - Catmandu modules for working with MARC data
 
 # MODULES
 
+- [Catmandu::MARC::Tutorial](https://metacpan.org/pod/Catmandu::MARC::Tutorial)
 - [Catmandu::Importer::MARC](https://metacpan.org/pod/Catmandu::Importer::MARC)
 - [Catmandu::Exporter::MARC](https://metacpan.org/pod/Catmandu::Exporter::MARC)
 - [Catmandu::Fix::marc\_map](https://metacpan.org/pod/Catmandu::Fix::marc_map)

lib/Catmandu/Exporter/MARC/ALEPHSEQ.pm

@@ -40,6 +40,10 @@ An ARRAY of one or more fixes or file scripts to be applied to exported items.
 
 Binmode of the output stream C<fh>. Set to "C<:utf8>" by default.
 
+=item default_fmt
+
+Set the value of the default C<FMT> field when none is given. Set to C<BK> by default.
+
 =back
 
 =head1 METHODS
@@ -63,8 +67,9 @@ our $VERSION = '1.18';
 with 'Catmandu::Exporter', 'Catmandu::Exporter::MARC::Base';
 
 has record               => (is => 'ro' , default => sub { 'record'});
-has record_format        => (is => 'ro', default => sub { 'raw'} );
+has record_format        => (is => 'ro' , default => sub { 'raw'} );
 has skip_empty_subfields => (is => 'ro' , default => sub { 0 });
+has default_fmt          => (is => 'ro' , default => sub { 'BK'} );
 
 sub add {
     my ($self,$data) = @_;
@@ -73,11 +78,18 @@ sub add {
         $data = $self->_json_to_raw($data);
     }
 
-    my $_id    = sprintf("%-9.9d", $data->{_id} // 0);
+    my $id_str = $data->{_id};
+    $id_str    =~ s{\D}{0}g if defined $id_str;
+    my $_id    = sprintf("%-9.9d", $id_str // 0);
 	my $record = $data->{$self->record};
 
     my @lines = ();
 
+    # Check required FMT field
+    if (@$record > 0 && $record->[0]->[0] ne 'FMT') {
+        push @lines , join('',$_id, ' ' , 'FMT', ' ', ' ' , ' L ' , $self->default_fmt);
+    }
+
     for my $field (@$record) {
         my ($tag,$ind1,$ind2,@data) = @$field;