What about this one:

my @ndates = qw(
                 02/01/2009 
                 01/31/2009 
                 01/01/2009 
                 01/31/2009 
                 02/20/2009 
                 02/20/2009 
                 02/20/2009 
                 02/20/2009 
                 02/01/2009
                 
                 );

my %counts = ();

for (@ndates) {
 $counts{$_}++;
}
foreach my $keys (sort keys %counts) {
   print "\n\n$counts{$keys}= $keys\n";
 }
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