Dim A.s(3)
Dim B.s(3)

A(0)="John": A(1)="Bob": A(2)="Mary": A(3)="Serena"
B(0)="Jim":  B(1)="Mary":B(2)="John": B(3)="Bob"

For a=0 To ArraySize(A())    ; A-B
  For b=0 To ArraySize(B())
    If A(a)=B(b)
      Break
    ElseIf b=ArraySize(B())
      Debug A(a)
    EndIf
  Next b
Next a

For b=0 To ArraySize(B())     ; B-A
  For a=0 To ArraySize(A())
    If A(a)=B(b)
      Break
    ElseIf a=ArraySize(A())
      Debug B(b)
    EndIf
  Next a
Next b