The partial content of a field can be yanked into one or more fields using a regular expression with group matching.
The field that has been yanked is replaced by fields representing the groups in the regular expression being yanked where round brackets are used to express the group positions. Fields appear in the same order as their corresponding groups and groups are ordered by the order of their opening brackets. For example, “.*(\d)(\d).*” will extract the two digits at the middle of a yanked field into two separate fields.
If you wish to retain the whole field, express the whole field as a group. For example “(.*(\d)(\d).*)” will generate 3 fields with the first field containing the whole of the yanked field.
By default, no fields are yanked.
See the Regular expression reference for details about regular expression notation.