I have a strange problem here. It seems that according to timegm from Time::Local there was no August 31 in 2009: The following three lines of code produce the output right after it: 
use Time::Local;
(...)
next unless (m{^(\d{4})-(\d\d)-(\d\d)$});
print "$3.$2.$1\n";
$next = timegm(0,0,0,$3,$2,$1-1900);

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Output: 
31.08.2009
Day '31' out of range 1..30 at /home/bjoern/bin/search.pl line 18

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Could anyone explain that please?

In reply to timegm: There is no August, 31 in 2009 by Rabenschwinge

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