A quick pass through B::Deparse explains what's happening:

perl -MO=Deparse,-p                                 < 1 > 17:18:46
$mech->cookie_jar->set_cookie(-name=>'PersistentZipCode',
                   -value=>'15213',
                           -host=>'www.kbb.com',
                       -expires=>'Thu, 04 Dec 2008 18:23:16 GMT',
                   -path=>'/'
                -secure=>'false');
$mech->cookie_jar->set_cookie((-'name'), 'PersistentZipCode', (-'value
+'), '15213', (-'host'), 'www.kbb.com', (-'expires'), 'Thu, 04 Dec 200
+8 18:23:16 GMT', (-'path'), ('/' - 'secure'), 'false');
[download]

I couldn't explain exactly why it's picked this way to parse, but you can see what's happened and why it's not throwing a syntax error though.