Just checked Agent, the code at the start should be "subject: (". There are also regular expressions that may upset the global search so in this program quote marks will actually work.

Example:-

subject: ("g_chifi3" or "g_kaiju" or "g_kof99" or "g_sdk993" or "s_alsynj" or "s_ariel" or "s_astrof" or "s_bankpa" or "s_bnzabr")

In the above example the quotes are not needed because there's no regular expressions as it's a nice and simple shortname.