Sub UUIDv4 As String
  Dim sb As StringBuilder
  sb.Initialize
  For Each stp As Int In Array(4, 4, 4, 4)
    If sb.Length > 0 Then sb.Append("-")
    For n = 1 To stp
      Dim c As Int = Rnd(0, 16)
      If c < 10 Then c = c + 48 Else c = c + 55
      If sb.Length = 19 Then c = Asc("8")
      If sb.Length = 14 Then c = Asc("4")
      sb.Append(Chr(c))
    Next
  Next
  Return sb.ToString.ToLowerCase
End Sub

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