“Camel case” is the capitalisation system preferred by Java and many other programmers – classes are capitalised e.g.
FooBar, while members have a lower case initial e.g.
It seems like Groovy may be trying to enforce this or something like it, and that is what is causing my BINSIC code to fail – as I have put PRINT all in capitals (as in BASIC), it is being treated much less flexibly than if it were lower case. Indeed the issue seems to be the capitalisation of the first letter.
I have not read anywhere of this as a mandatory piece of the language and so it looks like a bug to me.