Hi,

looking at the code of Memoize::Expire on line 56 of the current version

$self->{C}{$key} = $header . $value;
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let me assume that there is a bug or it was never intended to use this module in list context. In your case $value is an array ref, which gets stringified by this operation. When fetching this value you get the error you presented.

I'm sorry, but in this case I can only cite the man page to this module

This module is experimental, and may contain bugs. Please report bugs to the address below.

Best regards
McA