D Documentation  
rfind
int rfind(rchar[] string, char[] pattern, char[] attributes = null)

Search string for the last match with pattern with attributes. Returns the index in string of the match if found, -1 if no match.

Example:
import std.stdio;
import std.regexp;

int main() {
  // find the index of the last capitalized word
  char[] str = "I think next Tuesday is Sarah's birthday.";
  int index = rfind(str,"[A-Z][a-zA-Z']*");
  if(index != -1) {
    writefln("Index: %d",index);
  } 
  else {
    writefln("Not found");
  }
  return 0;
}

Output:
Index: 24
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