教えてください。恥ずかしいんですが...

sample.html
--------------------
<html>
2009-03-20
</html>
--------------------

yyyy-mm-dd.pl
--------------------
#!/usr/bin/perl

use Time::Local;

($s, $mi, $h, $d, $mo, $y, $w) = localtime(time);

$lastupdate = sprintf("%04d-%02d-%02d", $y + 1900, $mo +1, $d);
$yesterday = sprintf("%04d-%02d-%02d", $y + 1900, $mo +1, $d-1);

s/$yesterday/$lastupdate/g sample.html;
--------------------