@@ -, +, @@ --unless-exists --- misc/add_date_fields_to_marc_records.pl | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/misc/add_date_fields_to_marc_records.pl +++ a/misc/add_date_fields_to_marc_records.pl @@ -138,7 +138,11 @@ For instance: =item B<--unless-exists> -Will only create the new fields if this field does not exist +Will only create the new fields if this field does not exist. + +For instance, if --field='905$a=0/%Y' and --unless-exists='905$a' are provided, a 905$a will be created unless there is already one. +If --unless-exists is not passed, a new 905$a will be created in any case. + =back --