array of file handles in Perl

I used the following code today which creates, prints to and closes an array of file-handles using the IO::File core module. I had over 100K of files in the same directory and had to process them (and send them into their own directory too, but that is trivial). This works on Perl 5.14...

#==========================
# Andrew Cave
# 29 aug 2012
# 
#==========================

use IO::File;
#create a blank hash of day values
my %month=( 
'20120712' => '','20120713' => '','20120714' => '',
'20120715' => '','20120716' => '','20120717' => '',
'20120718' => '','20120719' => '','20120720' => '',
'20120721' => '','20120722' => '','20120723' => '',
'20120724' => '','20120725' => '','20120726' => '',
'20120727' => '','20120728' => '','20120729' => '',
'20120730' => '','20120731' => '','20120801' => '',
'20120802' => '','20120803' => '','20120804' => '',
'20120805' => '','20120806' => '','20120807' => '',
'20120808' => '','20120809' => '','20120810' => '',
'20120811' => '','20120812' => '','20120813' => '',
'20120814' => '','20120815' => '','20120816' => '',
'20120817' => '','20120818' => '','20120819' => '',
'20120820' => '','20120821' => '','20120822' => '',
'20120823' => '','20120824' => '','20120825' => '',
'20120826' => '','20120827' => '','20120828' => '' 
);
my ($key,$val) ;
#open a filename based on the array values and
#put the file-handle reference in the hash, using the dayvalue 
#as the key

while (  ($key,$val) = each(%month)) {
 my $filename = "output_$key.dat";
 my $fh = IO::File->new("> $filename") 
      or die "failed to create $filename $@\n$!\n";
 $month{$key} = $fh;
};

open IN , '<', 'input.dat';
while(){
 chomp;
 my $line = $_;
 if(/\d{8}/){# if the line has an eight digit number
   my $day = $1; 
   my $fh = $month{$day}; # get the correct filehandle
   print {$fh} "$line\n" ; #print to the filehandle - note the braces
                #move the file into its own directory
                #and add '.done' to the name
  if(! -d "./$day/"){
   system("mkdir ./$day/");
  }
  #print "$file|./$day/\n"; # the mv statements (if we want a record)
  system("mv $file ./$day/$file.done");

 }

}
close IN;

#close the array of files we created
# using IO::File
while (($key,$val)=each(%month)){
 my $close_fh =  $month{$key};
 $close_fh->close();
}