- irregex-match-substring <match> #!optional <index-or-name>procedure
- irregex-match-start-index <match> #!optional <index-or-name>procedure
- irregex-match-end-index <match> #!optional <index-or-name>procedure
Fetches the matched substring (or its start or end offset) at the given submatch index, or named submatch. The entire match is index 0, the first 1, etc. The default is index 0.
Returns #f if the given submatch did not match the source string (can happen when you have the submatch inside an or alternative, for example).