Excellent! -- thank you. I tried testing this, but couldn't get a version mis-match to cause a compile time error.
Then I decided to get into the debugger to have a better look at what was going on -- and the debugger issued the expected error right away. I'm not sure why, but I suspect it's the difference between what stage of the preparation the Perl internals got to in each situation. The debugger gets much closer to run-time, hence it triggered the error.
Alex / talexb / Toronto
Thanks PJ. We owe you so much. Groklaw -- RIP -- 2003 to 2013.