Write a file using a namelist.
<value> specifies the unit number. The keyword and equals sign are optional if it is the first item in the list.
The keyword and equals sign are optional if this is the second item in the list.
<variable> will contain zero if the operation was successful, otherwise a positive value to indicate an error, -1 to indicate EOF or -2 to indicate EOR.
<label> specifies a label to go to in the event of an error.