%dat_mapping = ();
%eng_mapping = ();

##</code><code>##

foreach my $file_name (key (%dat_mapping)) {
    print "blah\n";
}

##</code><code>##

foreach my $file_name (key (sub { if ($hash_name eq 'dat') {
                                       return \%dat_mapping;
                                  } else {
                                       return \%eng_mapping:
                                  }
                                 } ) {

            print "blah\n";
           
          }