Add an optional delimiter parameter to MARC::Field->as_string

An optional delimiter parameter is added. Current behaviour is preserved.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
follow up on MARC::Field->as_string() patch

- remove // so that compatibility with Perl 5.8 can be
  maintained
- add test case for new behavior

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
RT#88682: make delete_subfield() accept regexp for specifying subfields to delete

The following contruct can now be used:

  # delete any subfields whose labels ore neither
  # lowercase letters nor digits
  $field->delete_subfield(code => qr/[^a-z0-9]/);

Based on a patch by Jason Stephenson <jstephenson@mvlc.org> with a test
case written by myself.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
fix bug that prevented $field->as_string('0') from doing the right thing

$field->as_string('0') should return only the contents of
subfield $0, but instead returned the contents of all
subfields in the field.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
use warnings pragma throughout MARC::Record

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
prepare for MARC::Record 2.0.6

Signed-off-by: Galen Charlton <gmc@esilibrary.com>