The Insert Token button on the Create panel makes it easy to insert the following replacement text tokens that reinsert (part of) the subject string. See the Insert Token help topic for more details on how to build up a replacement text via this menu.
The three subject string tokens are only supported by a few replacement text flavors. They’re generally not very useful in search-and-replace operations. However, they can be quite handy when collecting or extracting text based on regex matches.
Insert a token into the replacement text that will be substituted with the text in the subject string to the left of the regular expression match. For example, when \d+ matches 123 in abc123def, then the part of the subject to the left of the match is abc.
Insert a token into the replacement text that will be substituted with the text in the subject string to the right of the regular expression match. For example, when \d+ matches 123 in abc123def, then the part of the subject to the right of the match is def.
Insert a token into the replacement text that will be substituted with the whole string that you applied the regular expression to, regardless of which part of it the regular expression actually matched.