$mday = sprintf('%02d', $mday) ;  # Not used in this script, but ret
+urns a 2 digit day
        $mon  = sprintf('%01d', ++$mon) ; # Returns a 1 digit month un
+til we get to 10 then use 2, not my choice.
        $year = 1900 + $year ; # Returns a 4 digit year
        $outdir = "_" . $year . "\\" . $mon . "\\" ; # Build the direc
+tory name based on date where the file is going \_2011\9\
[download]

Even simpler is (which replaces some of the code above that also):

my $ym = Time::Piece->new($mtime)->strftime("%Y\\%m");

# For single digit month:
$ym =~ s/0(\d)$/$1/;

my $outdir = "_$ym\\";
[download]

Update: Although in the OP I now notice that a single digit month (where possible) is required...so a further tweak would be required to this (updated again to reflect this).