The Classic C Quine (2003)

This is an Excel macro that is self-aware: it only tries to print itself if it is a quine.

It's sensitive to whitespace, so I provided the pastebin link above.

  Sub selfCheckingExcelQuine()
      s = "Sub selfCheckingExcelQuine()\    s = ~\    result = Replace(Replace(Replace(s, Chr(36), Chr(34)), Chr(92), vbCrLf), Chr(126), Chr(34) & s & Chr(34))\    \    If myText() = result Then\        Debug.Print result\    Else\        Debug.Print $Not a quine!$\    End If\End Sub\\Function myText()\    Dim p As VBProject: Set p = ThisWorkbook.VBProject\    Dim m As CodeModule: Set m = p.VBComponents(p.VBE.SelectedVBComponent.Name).CodeModule\    \    myText = m.Lines(1, m.CountOfLines)\End Function\"
      result = Replace(Replace(Replace(s, Chr(36), Chr(34)), Chr(92), vbCrLf), Chr(126), Chr(34) & s & Chr(34))
      
      If myText() = result Then
          Debug.Print result
      Else
          Debug.Print "Not a quine!"
      End If
  End Sub
  
  Function myText()
      Dim p As VBProject: Set p = ThisWorkbook.VBProject
      Dim m As CodeModule: Set m = p.VBComponents(p.VBE.SelectedVBComponent.Name).CodeModule
      
      myText = m.Lines(1, m.CountOfLines)
  End Function

That is undefined behaviour! (https://port70.net/~nsz/c/c11/n1570.html#J.2)