in reply to Re^4: How can you check to see if a file handle is already open?
in thread How can you check to see if a file handle is already open?

This is quite the same technique that chaos_cat suggested before, just a bit more inefficient, since 
print  { $file_handles{$date} } "$_\n";

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can be put outside the conditional opening of the file.

In Section Seekers of Perl Wisdom