Module for a Str-like regular expression syntax. The difference can be summarised as follows.
Theses functions are similar to Str.
regexp_match ?sem r t i tries matching
r and substrings
t beginning from
i. If match successes,
Some g is
g is the array containing the matched
n-th group in the
The matched string of the whole
r is stored in the
If matching fails,
None is returned.