Matching sub-strings
re-find
returns the first match within the string, using return values similar to re-matches.
nil
is returned when the pattern does not find a match.
(re-find #"pump" "Halloween")
A matching pattern without groups returns the matched string
(re-find #"e+" "Halloween")
Match with groups returns a vector of results
(re-find #"s+(.*)(s+)" "success")