And the fourth paragraph elaborates:

    If LIMIT is specified and positive, it represents the maximum
    number of fields the EXPR will be split into, though the actual
    number of fields returned depends on the number of times
    PATTERN matches within EXPR.  If LIMIT is unspecified or zero,
    trailing null fields are stripped (which potential users of
    "pop" would do well to remember).  If LIMIT is negative, it is
    treated as if an arbitrarily large LIMIT had been specified.