unfortunately not that simple!

if (exists $hash{absum}{absum})
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Ah, yes. But note how that syntax implies a -> operator, as ikegami described elsewhere in this thread, and it is that operator which makes $hash{absum} come into existance. Of course it is funny to see how exists still thinks $hash{absum} doesn't exist, however, not so funny anymore when you realize that exists really tries to check the existance of $hash{absum}->{absum} here. So exists is right and the information in that print statement is factually wrong. It should state print "Absum->absum doesn't exist\n" or something similar meaning the same.