Thank you! That made a lot of sense! Since it was not getting defined i couldn't compare my keys to undefined value. I changed it to

foreach $key(@key2) {
    $sysdef = $current{$key}{"nodesysoid"};
    if (exists $lookup{$sysdef}){
        #print "$key, $sysdef, $lookup{$sysdef}{name}, $source\n";
    }
}
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