regexp_matches() quantified-capturing-parentheses oddity

Hi all,

  wisu-dev=# SELECT regexp_matches('quux@foo@bar.zip', '([@.]|[^@.]+)', 'g');
   {quux}
   {@}
   {foo}
   {@}
   {bar}
   {.}
   {zip}

So far, so good.  However, can someone please explain the following to me?

  wisu-dev=# SELECT regexp_matches('quux@foo@bar.zip', '([@.]|[^@.]+)+', 'g');
   {p}

  wisu-dev=# SELECT regexp_matches('quux@foo@bar.zip', '([@.]|[^@.]+){1,2}', 'g');
   {@}
   {@}
   {.}
   {p}

  wisu-dev=# SELECT regexp_matches('quux@foo@bar.zip', '([@.]|[^@.]+){1,3}', 'g');
   {foo}
   {.}
   {p}

What's going on here??

Regards,

-Julian Mehnle