'die' concatenates its argument like print does. This is so that you can say e.g.

die "Expected ", scalar (@ref), " arguments, got ", scalar (@arr), "\n
+";
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rather than having to explicitly concatenate the strings:

die "Expected " . scalar (@ref) . " arguments, got " . scalar (@arr) .
+ "\n";
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The downside to this is that the args are obviously also concatenated when you pass the to a handler.

pike