If LIMIT is omitted (or, equivalently, zero), then it is usually treated as if it were instead negative but with the exception that trailing empty fields are stripped (empty leading fields are always preserved); if all fields are empty, then all fields are considered to be trailing (and are thus stripped in this case). Thus, the following: print join(':', split(',', 'a,b,c,,,')), "\n"; produces the output 'a:b:c', but the following: print join(':', split(',', 'a,b,c,,,', -1)), "\n"; produces the output 'a:b:c:::'.