get next argument. Skip past all []s and the BYREF symbol
#IF (!0>0) #IFADIM !1 DEFINE_NEXT_ARGUMENT !2 !3 !4 !5 !6 !7 !8 !9 #ELSE #IFSAME !1 BYREF DEFINE_ARGUMENTS !3 !4 !5 !6 !7 !8 !9 #ELSE DEFINE_ARGUMENTS !2 !3 !4 !5 !6 !7 !8 !9 #ENDIF #ENDIF #ENDIF