Please, oh esteemed monks of perl, grace me with your wisdom!

I have these two lines:

    my $poptags = $memcache->get('poptags');
    my @poptags = @{$memcache->get('poptags')};
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Now, print Dumper($poptags) is UNDEF and print Dumper(@poptags) is the array I was looking for.

This began happening at 8:42am, before anyone got to work. Nothing on the machine (besides logs) have modification times newer than two weeks ago. What would be causing this, if the memcache daemon is also local?