It seems that executing the script whilst running a debug build via Visual Studio caused ActiveState's Perl to run rather than the version I was supposed to be using, indicating a path issue.
In the future, when something "suddenly stops working" and "I haven't changed anything", look to see if you actually have changed something (like the processing environment).

In reply to Minor nitpick by proceng
in thread Bitwise & stopped working? by Krokus

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