       ("abbbe", nil),
       ("accce", nil),
       ("abcbbd", nil))
+    flatCaptureTest(
+      #"(?:\w\1|:(\w):)+"#,
+      (":a:bacada", ["a"]),
+      (":a:baca:o:boco", ["o"]),
+      ("bacada", nil),
+      (":a:boco", ["a"])          // this matches only the ':a:' prefix
+    )
   }
 
   func testMatchReferences() {

  syntax: SyntaxOptions = .traditional,
  enableTracing: Bool = false,
  dumpAST: Bool = false,
  xfail: Bool = false
) {
  for (test, expect) in tests {
    do {

      }
    } catch {
      if !xfail {
        XCTFail("\(error)", file: file, line: line)
      }
    }
  }
