From "The Oberon Programming Language"[0]: "Capital and lower-case letters are considered as being distinct....These reserved words consist exclusively of capit

From "The Oberon Programming Language"[0]: "Capital and lower-case letters are considered as being distinct....These reserved words consist exclusively of capital letters and cannot be used in the role of identifiers". So it seems that keywords do need to be in all-caps, at least if your compiler is compatible with Wirth's description (the standard?). [0]: https://people.inf.ethz.ch/wirth/Oberon/Oberon07.Report.pdf https://people.inf.ethz.ch/wirth/Oberon/Oberon07.Report.pdf