Function builtin_regmatches 

fn builtin_regmatches(
    args: &[RValue],
    _: &[(String, RValue)],
) -> Result<RValue, RError>

Extract matched substrings from regexpr/gregexpr results.

@param x character vector that was searched @param m match data from regexpr() or gregexpr() @return character vector (for regexpr) or list (for gregexpr) of matched substrings