There are lots of ways to do this, (some listed above by others).
One thing I can see wrong with your code is you are calling

localtime
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more than once. This can lead to inconsistancies in the numbers. For formatting, try this:

my @time = localtime;
my $yyyy = $time[5] + 1900;
my $mm = sprintf("%02d", $time[4] + 1); # pad with 0's
# repeat for other variables
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