I like my code to be readable so I like to use ingroup like the following.
 Code:
If InGroup("group1") or InGroup("group2")
  use M: 
endif


However, ingroup supports mulitple groups, here are some other examples:

 Code:
If InGroup("Developers", "Testers") = 1
   ? "Member of Developers OR Testers group"
EndIf

If InGroup("Developers", "Testers", 1) = 1
   ? "Member of Developers AND Testers group"
EndIf

$Array = "Developers", "Testers"
If InGroup($Array, 1) = 1
   ? "Member of Developers AND Testers group"
EndIf