$ perl -le'
$year = 111;
$mon = 7;
$outdir = "_" . ($year+=1900) . "\\" . ($mon+=1) . "\\";
print $outdir;                                          
'
_2011\8\
$ perl -le'
$year = 111;
$mon = 7;
$outdir = "_" . ($year+1900) . "\\" . ($mon+1) . "\\";
print $outdir;
'
_2011\8\