Maybe it's a new warning? (From 5.8.4):

Scalar value @REALM[1] better written as $REALM[1] at ...
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Also, I'm just guessing the OP is using neither strict nor warnings. If he was using warnings, he'd be getting a warning and probably fixing it, and he'd probably already be using strict. If he does start using strict and warnings, then I bet there will be a bunch of errors to fix (and a good chance that either version of that line will need to be fixed).